Network Attached Storage Introduction

What is NAS (Network Attached Storage)

In a NAS architecture, corporate information resides in a storage system that is attached to a dedicated server, which in turn is directly connected to a network, and uses a common communications protocol, such as TCP/IP. In a corporate IT infrastructure, the NAS operates as a server in a typical client/server environment. The NAS is connected to a network by standard connectivity options such as Ethernet, FDDI and ATM. In some cases, a single specialized NAS server can have up to 30 Ethernet connections.

A NAS server (a processor with an operating system) is necessary in order to transfer the data between it and the NAS storage device, and then move the data on to the corporate network. This is done via traditional file I/O protocol. The most common of these protocols are Network File System (NFS) and Common Internet File Service (CIFS).

NFS was originally developed by Sun Microsystems and is now part of the Open Network Computing (ONC) initiative. It is the most common file access protocol to access shared files in a UNIX environment. CIFS is a file access protocol designed for the Internet, and based on the Server Message Block (SMB) protocol used by the Microsoft Windows operating system. CIFS does not replace the use of NFS, but rather complements it, because of its ability to provide synchronization between client and server.

Although a NAS with NFS can be implemented on readily available tightly-coupled server and disk storage arrays, there are actually only three (3) major vendors that currently have a large marketshare of the NAS marketspace. They are: Network Appliance (also known as NetApps), Auspex Systems, and Sun Microsystems. Both NetApps and Auspex use proprietary tightly integrated servers and storage devices. In the majority of cases, the Sun implementation uses a dedicated Sun server, and typically connected to external Sun storage; although any external storage that is certified to be connected to a Sun server can also be used. However, this is not the case with NetApps or Auspex, as additional storage requirements must be acquired from the respective NAS vendor.

The NAS server permits multiple clients to share files, since clients can access files as if they were local files, with the exception that they must be accessed over a network. In this way, common files can be maintained in a central location, and accessed by many clients, which eliminates the need for multiple copies of files on multiple client systems. In addition, this improves data integrity, data security and reduces costly duplication of files. Major applications that benefit from the use of NAS to share large amounts of information include CAD/CAM (Computer Aided Design/Computer Aided Manufacturing), document management, imaging as well as other similar application serving environments.


Because data travels over the network, NAS is not always suitable for applications such as data warehouses and On-Line Transaction Processing (OLTP), since these applications need to sustain high I/O data rates with little, or no degradation in response times to the clients.

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Interview questions series 10
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Network Attached Storage Videos,Tutorial & Interview questions

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Here are some real informative Videos on Network attached Storage & some more interview questions on NAS.

Some of the more general yet essential interview questions on NAS are:
1.What is NAS?
2.When NAS is a better solution as a storage requirement?
3.Whats the difference between NAS & SAN ?
4.What are the advantages & Disadvantages of NAS ?
5.How can a NAS implementation be improved over performance ?
6.Mention some case study on NAS implementation ?
7. Is it possible to setup a NAS using very basic PC equipment ?
8. Which are the best NAS vendors & what are their focu products?
9. How NAS-DAS-SAN differ ?
10. Can u explain a NAS Gateway in detail ?

Answers for all these questions will follow in next posting with more photos & Videos.

Answers to Interview Questions on Veritas Volume Manager

EMAIL roger.smithson@gmail.com & GET FREE SAN TUTORIAL GUIDE.(PDF:124 PAGES)

Thanks to Ashish Pathak for all the questions and also answers to Interview questions on Veritas Volume Manager.

# Name the mandatory disk group in VxVM 3.5 ? How will you configure VxVM in 3.5 ?
ANS: rootdg is the mandatory disk group in VxVM 3.5, vxinstall is the command to configure VxVM, It will create the disk groups, initializes the disks and adds them to the group.

# How will you create private and shared disk group using VxVM ?
ANS: For Private DG:
Command: vxdg init

For Shared DG:
Command: vxdg -s init < disk1 disk2 disk3 >

# Which are the different layouts for volumes in VxVM ?
ANS: mirror, stripe, concat (default one), raid5, stripe-mirror, mirror-stripe.

# What is the basic difference between private disk group and shared disk group ?
ANS: Private DG: The DG which is only visible for the host on which you have created it, if the host is a part of cluster, the private DG will not be visible to the other cluster nodes.
Shared DG: The DG which is sharable and visible to the other cluster nodes.

# How will you add new disk to the existing disk group ?
ANS: Run vxdiskadm command, which will open menu driven program to do various disk operations, select add disks option or you can use another command vxdiskadd.

# How will you grow/shrink the volume/file system ? What is the meaning of growby and growto options ? What is the meaning on shrinkto and shrinkby options ?
ANS: vxassist command is used to do all volume administration, following is the description and syntax.

Growby option: This is will grow your file system by adding new size to the existing file system.

Growto option: This will grow your file system as per the new size. This WILL NOT ADD new size to the existing one.

Shrinkby option: This will shrink your file system by reducing new size from existing file system.

Shrinkto option: This will shrink your file system as per the new size. This WILL NOT REDUCE the file system by reducing new size.

Command:
vxassist -g [growto, growby, shrinkto, shrinkby] length

# How will you setup and unsetup disks explicitly using VxVM ?
ANS: You can use /etc/vx/bin/vxdiskunsetup to unsetup the disk, and /etc/vx/vxdisksetup to setup the disk.

# How will you list the disks, which are in different disk groups ?
ANS: vxdisk list is the command will list the disks from the DG which is currently imported, you can check the same using vxprint command too. vxdisk -o alldgs list command list all the disks which are in different dg's.

# What is the private region in VxVM ?
ANS: Private region stores the structured VxVM information, it also stores the disk ID and disk geometry. In short words it has metadata of the disk.

# If, vxdisk list command gives you disks status as "error", what steps you will follow to make the respective disks online ?
ANS: If you faced this issue because of fabric disconnection then simply do vxdisk scandisks, otherwise unsetup the disk using using /etc/vx/bin/vxdiskunsetup and setup the disks again using /etc/vx/bin/vxdisksetup, this will definitely help! [ /etc/vx/bin/vxdiskunsetup will remove the private region from the disk and destroys data, backup the data before using this option]

I am greatly thankful to Ashish Pathak ashish.rp AT gmail.com for emailing & contributing this real interview questions on Veritas Volume Manager

Interview questions on Veritas Volume Manager

EMAIL roger.smithson@gmail.com FOR A FREE SAN STUDENT GUIDE PDF
Veritas Volume Manager Overview


Some good questions on VERITAS Volume Manager. Before asking these questions make sure that candidate is familiar with LVM or VxVM and knows the benefits of these tools over traditional partitioning/file system.

1. Name the mandatory disk group in VxVM 3.5 ? How will configure VxVM in 3.5 ?
2. How will you create private and shared disk group using VxVM ?
3. Which are the different layouts for volumes in VxVM ?
4. What is the basic difference between private disk group and shared disk group ?
5. How will you add new disk to the existing disk group ?
6. How will grow/shrink the volume/file system ? What is the meaning of growby and growto options ? What is the meaning on shrinkto and shrinkby options ?
7. How will you setup and unsetup disks explicitly using VxVM ?
8. How will list the disks, which are in different disk groups ?
9. What is private region in VxVM ?
10. If, vxdisk list command gives you disks status as "error", what steps you will follow to make the respective disks online ?

These are some questions which I feel every storage professional should know. Please let me know if these are useful, answers will be posted in coming posts.

THANKS ASHISH FOR CONTRIBUTING ABOVE INTERVIEW QUESTIONS ON VERITAS VOLUME MANAGER

Advantages of Reading this Blog Regularly - Blog is updated daily

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Netapp V-series device in a SAN

- This Blog is all about "YOU" Getting a Job.
- You Can Write/Contribute & Win Some COOL Stuff
- Know Basically What is Storage Area Network
- If You want a High Paying Job what should be your Strategy.
- It has more than 90 interview questions listed in this single blog
Interview questions series 1
Interview questions series 2
Interview questions series 3
Interview questions series 4
Interview questions series 5
Interview questions series 6
Interview questions series 7
Interview questions series 8
Interview questions series 9
Interview questions series 10
- Know what happens in office routine of a Storage professional
- Know what sort of job roles are there in Storage area networking
- Know what they ask in a storage job interview
- Need guidance to revamp or improve your Resume
- It has one simple storage implementation Case study
- Basic questions a Software job hunter asks
- Answers for the questions like Job Opportunities in Storage
- Want to see details of Job requirement for Storage
- U like to take a Virtual tour of Cisco Production Data Center
- Every one talks about HA or High Availability - should'nt You
- Dont forget that Career in Any field requires dedication and hard work - U can do it Dude

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Storage Area Networking Jobs Interview Questions

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Fibre Channel Network Adapter Card
(Host Bus Adapter- HBA)

Fibre Channel Cable

FC Cable in comparison with a Serial DB9 Cable

After listing more than 60 interview questions in the previous posts find below some listing of only questions from storage interviews. Answers for the same will be sent only through email if you contribute for this blog. Below questions are contributed by Jai one of the professional working in Real Storage Job who contributed this posting.

1)What is the most critical component in SAN?
2)What is the default id for SCSI HBA?
3)What is parallelism?
4)What do you know about SAN testing?
5)Explain a typical SAN landscape?
6)What is fan-in and fan-out in SAN Virtualization system?
7)How is the interoperability between the server and the storage is achieved?
8)What are the performance metrics of SAN?
9)What do you know about I/O meters , their types and how are the used?
10)What is the equivalent of Address resolution protocol in storage?
11)What is meant by availability & reliability in Storage ?
12)What is Disaster Recovery & how it is implemented in a Storage environment?
13)Example for failover cluster configurations ?
14)What are the needs/advantages of Storage consolidation ?

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Storage area networking Interview Questions

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Some more interview questions contributed by Jai
51) What is one of the constrains of using storage switch?
Latency

52) What is the difference between NAS and SAN?

NAS
Cables used in the n/w
n/w protocols (TCP/IP, IPx) and file sharing protocols (IFS & NFS)
Lower TCO
Support heterogeneous clients
Slow

SAN
High-speed connectivity such as FC
Do not use n/w protocols because data request are not made over LAN
Higher TCO
Requires special s/w to provide access to heterogeneous clients
Fast

53) What is Jitter?
Jitter refers to any deviation in timing that a bit stream suffers as it traverses the physical medium and the circuitry on-board the end devices. A certain amount of deviation from the original signaling will occur naturally as serial bit stream propagates over fibre-optic or copper cabling.

Mainly caused by electro magnetic interference

54) What is BER/Bit error rate?
Probability that a transmitted bit will be erroneously received is the measure of number of bits (erroneous) at the output of the receiver and dividing by the total number of bits in transmission.

55) What is WWPN?
WWPN is the 16bit character that is assigned to the port, SAN volume controller uses it to uniquely identify the fibre channel HBA that is installed in the host system.

56) What is connection allegiance?
Given multiple connections are established, individual command/response pair must flow over the same connection. This connection allegiance ensures that specific read or writes commands are fulfilled without the additional overhead of monitoring multiple connections and to see whether a particular request is completed.

57) What is burst Length?
The burst length is the number of bytes that the SCSI initiator sends to the SCSI target in the FCP_DATA sequence.

58) Explain different types of RAID?
RAID 0: data striping blocks are written sequentially, no redundancy, high performance than single disk access.

RAID 1: Mirroring, data blocks written to both disk at once, 100% redundancy, 100% additional capacity required. Read can be distributed across both the disks to increase performance.

RAID 3: Striping with byte parity, adds parity information to rebuild data in the event of disk failure, high transfer rate and availability with lower capacity required than RAID 1. Transactions performance low because all disks operate in lock step.

RAID 4: striping with block parity, independently accessible disks, data blocks written sequentially to each disk failure. Dedicated parity disk is write bottleneck and leads to poor performance.

RAID 5: Striping with rotational parity, parity blocks written per row and distributed across all disks, parity distribution eliminates single write bottleneck overhead for parity calculation on write supplemented with parallel microprocessors or caching.

59) What is NAS in detail ?
NAS or Network Attached Storage
“NAS is used to refer to storage elements that connect to a network and provide file
access services to computer systems. Abbreviated NAS. A NAS Storage Element consists of an interface or engine, which implements the file services, and one or more devices, on which data is stored.
NAS elements may be attached to any type of network. When attached to SANs, NAS elements may be considered to be members of the SAS (SAN Attached Storage) class of storage elements.

A class of systems that provide file services to host computers. A host system that uses network attached storage uses a file system device driver to access data using file access protocols such as NFS or CIFS. NAS systems interpret these commands and perform the internal file and device I/O operations necessary to execute them.”

Though the NAS does speed up bulk transfers, it does not offload the LAN like a SAN does. Most storage devices cannot just plug into gigabit Ethernet and be shared - this requires a specialized file server the variety of supported devices is more limited.NAS has various protocols established for such needed features as discovery, access control, and name services.

60)Briefly list the advantages of SAN ?
SANs fully exploit high-performance, highconnectivity network technologies
SANs expand easily to keep pace with fast growing storage needs
SANs allow any server to access any data
SANs help centralize management of storage resources
SANs reduce total cost of ownership (TCO)

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Storage jobs interview questions from real interview experiences

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Simple interview questions with very simple answers from Real Storage Job interviews : Contributed by Jai

I would request you all to contribute any text,post,article for this blog & help the people struggling for a Job in Networking,Storage,System administration - You will get more than 200 interview questions inreturn for your contribution.

Some more interview questions are listed below
40) What is Exchange in FC(Fibre Channel)?
Exchange is to establish a relationship between 2 N_PORTs and then these two ports transfer data via one or more sequence within this relationship.
Example: Exchange exist to transfer the command, data and the status of one SCSI task

41) Why do we need Login in FC?
Port Login: To exchange service parameters between N_Ports and N_Ports
Process Login: To establish the SCSI operating environment between two N_PORTS

42) What are the different types of clusters?
a) High availability clusters
b) High Performance Clusters
c) Load Balancing Clusters.

43) What are three levels of management in storage?
a) Storage Level Management
b) Network Level Management
c) Enterprise Level Management.

44) What are the key activities in SAN management?
a) Monitoring
b) Configuring
c) Controlling
d) Troubleshooting
e) Diagnosing

45) What is the difference between HBA and NIC?
HBA => Host bus adapters are used in storage based traffic while NIC (Network Interface Cards are used in IP based LAN traffic.

46) What is the measuring unit of data activity?
Gigabits per hour

47) What are the basic storage policies?
a) Security and authentication
b) Capacity, Content and quota management
c) Quality of Service

48) What is bypass circuitry?
A circuit that automatically removes the storage device from the data path (FC device out of FC AL loop) when signaling is lost (this signal is called port by-pass signal).

49) Explain different classes of service in FC?
Class 1: dedicated connection between two communicators with acknowledgement of frame delivery.
Class 2: is connection less but provides acknowledgement
Class 3: is connection less and provides no notification of delivery
Class 4: allows fractional bandwidth for virtual circuits
Class 5: Provides multicast with acknowledgment
Class F: Is used for switch to switch communication in the fabric.

50) How many connections are possible in Fabric topology?
2^24 (24 bit address to the port) , and the largest possible fabric will have 239 interconnected switches.

More than 40 interview questions on storage,san,nas,FC:Thanks Jai for this contribution

I want to thank Jai one of our blog reader who has contributed more than 58 interview questions from his experience of attending real storage interviews.

In the last 2 posts we had more than 30 interview questions posted which can be accessed through the below links
interview questions Series 1
interview questions Series 2

Here you get 10 more interview questions for storage area networking
31) What are tow types of recording techniques on the tapes?
a) Linear Recording
b) Helical Scan Recording.

32) What is snap shot?
A snapshot of data object contains an image of data at a particular point of time.

33) What is HSM?
Hierarchical storage management, an application that attempts to match the priority of data with the cost of storage.

34) What is hot-swapping?
Devices are allowed to be removed and inserted into a system without turning off the system.

35) What is Hot-Sparing?
A spare device is available to be inserted into the subsystem operation without having to remove and replace a device.

36) What are different types of backup system?
a) Offline
b) Online
c) Near Line

37) What is the different between mirroring, Routing and multipathing?

Redundancy Functions Relationships Role
Mirroring Generates 2 i/os to 2 storage targets Creates 2 copies of data
Routing Determined by switches independent of SCSI Recreates n/w route after a failure
Multipathing Two initiator to one target Selects the LUN initiator pair to use

38) Name few types of Tape storage?
a) Digital Linear Tape
b) Advanced Intelligent Tape
c) Linear Tape Open

39) What is a sequence in FC?
Group of one or more frames that encompasses one or more “information units” of a upper layer protocol.

Example:
It requires
i) One sequence to transfer the command
ii) One or more sequence to transfer the data
iii) Once sequence to transfer the status.

40) What is Exchange in FC?
Exchange is to establish a relationship between 2 N_PORTs and then these two ports transfer data via one or more sequence within this relationship.
Example: Exchange exist to transfer the command, data and the status of one SCSI task

Networking (Storage) interview questions contributed by Jai(series 2)

Continuing the previous posting here some more interview questions contributed by our blog reader Jai.
More than 20 real storage job interview questions were posted in the previous post.

21) What is the purpose of disk array?
Probability of unavailability of data stored on the disk array due to single point failure is totally eliminated.

22) What is disk array?
Set of high performance storage disks that can store several terabytes of data. Single disk array can support multiple points of connection to the network.

23) What is virtualization?
A technique of hiding the physical characteristics of computer resources from the way in which other system application or end user interact with those resources. Aggregation, spanning or concatenation of the combined multiple resources into larger resource pools.

24) What is Multipath I/O?
Fault tolerant technique where by there is more than one physical path between the CPU in the computer systems and its main storage devices through the buses, controllers, switches and other bridge devices connecting them.

25) What is RAID?
Technology that groups several physical drives in a computer into an array that you can define as one or more logical drive. Each logical drive appears to the operating system as single drive. This grouping enhances the performance of the logical drive beyond the physical capability of the drives.

26) What is stripe-unit-size?
It is data distribution scheme that complement s the way operating system request data. Granularity at which data is stored on one drive of the array before subsequent data is stored on the next drive of the array. Stripe unit size should be close to the size of the system I/O request.

27) What is LUN Masking?
A method used to create an exclusive storage area and access control. And this can be achieved bye storage device control program.

28) What is the smallest unit of information transfer in FC?
Frame

29) How is the capacity of the HDD calculated?
Number of Heads X Number of Cylinders X Sectors per track X Sector Size

30) What is bad block reallocation?
A bad sector is remapped or reallocated to good spare block and this information is stored in the internal table on the hard disk drive. The bad blocks are identified during the media test of the HDD as well as during various types of read write operations performed during the I/O tests. Apart from the new generation of HDD comes with a technology called BGMS (background media scan) which continuously scans the HDD media for defects and maps them when the drive is idle (this is performed after the HDD is attached to the system).

Real Interview Questions contributed by blog reader Jai

Hearty thanks to this blog's reader Jai who has contributed more than 58 interview questions from his experience of attending interviews for real company jobs.

I will be posting these questions in the subsequent blog postings - I rally appreciate his initiative and would request all other professionals or whoever - who have the knowledge to share it with the community and help the jobseekers.

1) What is the difference between RAID 0, RAID 1 and RAID 5?

RAID 0 => Plain striping typically with 24kb, 54kb or 128kb stripe size
RAID 1 => Mirroring
RAID 5 => Stripping with parity

2) Describe in brief the composition of FC Frame?
Start of the Frame locator
Frame header (includes destination id and source id, 24 bytes/6 words)
Data Payload (encapsulate SCSI instruction can be 0-2112 bytes in length)
CRC (error checking, 4 bytes)
End of Frame (1 byte)

3) What is storage virtualization?
Storage virtualization is amalgamation of multiple n/w storage devices into single storage unit.

4) What are the protocols used in physical/datalink and network layer of SAN?
a) Ethernet
b) SCSI
c) Fibre Channel

5) What are the types of disk array used in SAN?
a) JBOD
b) RAID

6) What are different types of protocols used in transportation and session layers of SAN?
a) Fibre Channel Protocol (FCP)
b) Internet SCSI (iSCSI)
c) Fibre Channel IP (FCIP)

7) What is the type of Encoding used in Fibre Channel?
8b/10b, as the encoding technique is able to detect all most all the bit errors

8) How many classes of service are available in Fibre Channel?
7 Classes of service

9) What are the main constrains of SCSI in storage networking?
a) Deployment distance (max. of 25 mts)
b) Number of devices that can be interconnected (16)

10) What is a Fabric?
Interconnection of Fibre Channel Switches

11) What are the services provided by Fabric to all the nodes?
a) Fabric Login
b) SNS
c) Fabric Address Notification
d) Registered state change notification
e) Broadcast Servers

12) What is the difference between LUN and WWN?
LUN: unique number that is assigned to each storage device or partition of the storage that the storage can support.
WWN: 64bit address that is hard coded into a fibre channel HBA and this is used to identify individual port (N_Port or F_Port) in the fabric.

13) What are the different topologies in Fibre Channel?
a) Point-to-Point
b) Arbitrary Loop
c) Switched Fabric Loop

14) What are the layers of Fibre Channel Protocol?
a) FC Physical Media
b) FC Encoder and Decoder
c) FC Framing and Flow control
d) FC Common Services
e) FC Upper Level Protocol Mapping

15) What is zoning?
Fabric management service that can be used to create logical subsets of devices within a SAN. This enables portioning of resources for management and access control purpose.

16) What are the two major classification of zoning?
Two types of zoning are
a) Software Zoning
b) Hardware Zoning

17) What are different levels of zoning?
a) Port Level zoning
b) WWN Level zoning
c) Device Level zoning
d) Protocol Level zoning
e) LUN Level zoning


18) What are the 3 prominent characteristics of SAS Protocol?
a) Native Command Queuing (NCQ)
b) Port Multiplier
c) Port Selector

19) What are the 5 states of Arbitrary Loop in FC?
a) Loop Initialization
b) Loop Monitoring
c) Loop arbitration
d) Open Loop
e) Close Loop

20) How does FC Switch maintain the addresses?
FC Switch uses simple name server to maintain the mapping table

Career in storage technology requires hardwork and dedication

If You are a Jobhunter & are planning to build your Career in Storage - know this first You Need to be dedicated , hard working and little guidance thats all it needs.

I have been recieving more than 30 emails everyday in respone to my blog & I am promptly replying each and every email - Because I want to HELP YOU GET A JOB. But just getting a Job is not the end of all miseries - believe me - Getting a Job is just 20% effort - Building Your Career & Growing in your Job is 80% effort. Jobseekers email me just asking for tutorials, materials, interview questions, quick help guide - I am happy to share them all but GUYS use them well - spend more than 4 to 6 hours a day with dedication learning these things, workingout on whatever little lab setup u can configure urself.

If you are really dedicated & willing to work hard - I can surely put time to help you to guide in you whatever time I can take.

Also DO CONTRIBUTE TO THIS BLOG by emailing roger.smithson@gmail.com any article, any interview experience, any troubleshooting or anything - WHICH is ORIGINAL & not copied from web. I want to help a COMMUNITY of Job seekers - Please help me to help them most.

Do care to give more than what u take from this blog because I highly appreciate your contribution & may send you more stuff to boost your Career.

Here is a Contest - You Can Win Loads of Interview Tips,Questions,Real interview experiences, Real Resumes of some of Known SAN professionals who have openly published their resume online & lots more - All u need to do is write & help people struggling out there to get some decent job.

INDEX of all latest blog articles to help you reach out for the info
This Blog is About "YOU" - How can I Help You Get That Job

Storage Jobs Blog Contest - You Can Easily Win

STRATEGY: Getting a High paying Storage JOB

Regular day in a Storage Professionals Office Life

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Cisco data center -You should have a look inside

Storage Switches in Cisco Central Network Lab

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Production Data Center of Cisco Virtual Tour : Modems

SAN,NAS,DAS real company interviews & jobs

Comments on Storage jobs blog are very much appreciated

How can I get entry into a Storage Area Networking Job ?

Storage job interview questions - for a starter

Looking for a Software Job - Find high paying Storage Job

Storage jobs Salary structure - How much they Pay This will be updated soon to contain an offer letter from a real storage company and also a salary structure from a real storage company.

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High Availability in Storage why is it so important

For anyone aspiring for a job in storage industry this is a very important concept which he needs to gain expertise in. Because HA is very very much essential in storage. Email roger.smithson@gmail.com for a FREE SAN Tutorial PDF and also FREE HA-in-Storage PDF - Email me so I can help you in your Job Hunt or any Career plans.

HA is the process of making sure your system whether it is a Single critical production server or a cluster of servers with the interconnecting network is Highly Available, round the clock 24 Hours X 7 days X 365 days usually referred as 24X7 HA.

An integral part of building large-scale, mission-critical systems that your business and your users can rely on is to ensure that no single point of failure can render a
server or network unavailable. There are several types of failures you must plan against to keep your system highly available.

Storage failures
There are many ways to protect against failures of individual storage devices using techniques such as Redundant Array of Independent Disks (RAID). Hardware solutions that support many different types of hardware redundancy for storage devices, allowing devices as well as individual components in the storage controller itself to be exchanged without losing access to the data. Software solutions also provide similar capabilities of storage redundancy.

Courtesy: Zibiz.com : Zistor Business continuity system


Network failures
There are many components to a computer network, and there are many typical network topologies that provide highly available connectivity. All types of networks need to be considered, including client access networks and management networks. In storage area networks (SANs), failures might include the storage fabrics that link the computers to the storage units.

Courtesy: ICANN.org : Database Operations (Storage Failure)


Computer or Server failures
Many enterprise-level server platforms provide redundancy inside the computer itself, such as through redundant power supplies and fans. Vendors allow components such as peripheral component interconnect (PCI) cards and memory to be swapped in and out without removing the computer from service. In cases where a computer fails or needs to be taken out of service for routine maintenance or upgrades, clustering provides redundancy to enable applications or services to continue. This redundancy happens automatically in clustering, either through failover of the application (transferring client requests from one computer to another) or by having multiple instances of the same application available for client requests.

Courtesy: Falconstor.com : Nearline Storage to Maximize Availability in a Data Center


Site failures
In extreme cases, a complete site can fail due to a total power loss, a natural disaster, or other unusual occurrences. More and more businesses are recognizing the value of deploying mission-critical solutions across multiple geographically dispersed sites. For disaster tolerance, a data center’s hardware, applications, and data can be duplicated at one or more geographically remote sites. If one site fails, the other sites continue offering service until the failed site is repaired. Sites can be active-active, where all sites carry some of the load, or active-passive, where one or more sites are on standby.

Plz keep coming back because this blog will be updated daily twice for more information on Storage area networking or Simply Storage jobs information.

Storage Area Networking Blog Contest - You Can Win

You Can Easily Win this Contest Because the contest is Simple

1. Write anything about Storage technology and send it to roger.smithson@gmail.com

Whats the Prize - Are you sure I can win :
1. 10 Top Storage Related Tutorials in PDF or DOC format will be emailed to you within 12 hours of your submission .
2. I will rewrite your Resume to make it more powerful to get you Interviews,Better pay and a Career Boost .
3. I will Guide you through emails for your Career progress .
4. Access to Storage Technology Video links which are not yet posted on this blog .

Your article will be posted on this blog after necessary modifications & You are helping a community of Job seekers by sharing the information.

You Can write about your experience with interviews, share some interview questions as well as interview tips, write about your experience with some of storage products or softwares , write about companies ,even feedback about this blog etc.

BUT MAKE SURE THAT U ARE SUBMITTING ORIGINAL CONTENT & NOT DUPLICATE FROM THE WEB OR ANYWHERE ELSE

This post is about "You" - How can I Help You Get That Job

This Blog is focussed on Helping You get a Job in Storage domain.

Till now I have written more than 23 posts about storage technology, interview tips, interview questions , how you can prepare , what are the job opportunities etc

But today I want to write about YOU.

I want to know from YOU
- What you would like to see on this blog
- What helps you get that Job you are aiming
- What is the information you are looking for
- What are the outlines or topics you want me to write about

Also can YOU tell me
- How you felt reading this blog
- What was bad and what was good
- What can be improved ( I know navigation is bad :(

Is there anyway YOU can contribute
- I know many people who visit this blog have quite a good experience , knowledge & many more things which they can share

Please write to me roger.smithson@gmail.com & I will reply you within 12 Hours. Thanks for taking time to read this blog.

Storage area networking Tutorial

Storage Types :

DAS : Direct Attached Storage : Server (or host)is directly connected to storage.


NAS : Network Attached Storage : NAS is essentially a file server which is connected to storage thru some network interface using widely supported IP protocols. NFS,CIFS are supported.


SAN : Storage Area Networking : Storage networks that connect multiple hosts through a switched fabric such as Fibre Channel or iSCSI.SAN is configured with multiple switches and multiple server Host Bus Adapters (HBA) to create a high-availability storage configuration and various RAID solutions are used to protect data at the disk level.


SEND AN EMAIL TO roger.smithson@gmail.com & recieve a FREE FULL FEATURED SAN Tutorial Guide.pdf with more than 124 pages . Boost for a Career in Storage.

Though many of Job hunters have good knowledge about DAS,NAS,SAN usually while answering some of the basic interview questions like

1. Differentiate between DAS-NAS-SAN
2. When NAS is a better option than DAS
3. When SAN is a better option than NAS
4. What are the advantages & disadvantages of each of these product types
(Above are Real Questions asked in a recent interview in one of the Storage test job interview)

Some more interview questions with brief answers

1. Name some of the SAN topologies
point-topoint,arbitrated loop, and switched fabric topologies

2. Whats the need for separate network for storage why LAN can not be used?
LAN hardware and operating systems are geared to user traffic, and LANs are tuned for a fast user response to messaging requests.
With a SAN, the storage units can be secured separately from the servers and totally apart from the user network enhancing storage access in data blocks(bulk data transfers), advantageuos for serverless backups.

3. What are the advantages of RAID ?
“Redundant Array of Inexpensive Disks”
Depending on how we configure the array, we can have the
- data mirrored [RAID 0] (duplicate copies on separate drives)
- striped [RAID 1] (interleaved across several drives), or
- parity protected [RAID 5](extra data written to identify errors).
These can be used in combination to delier the balance of performance and reliability that the user requires.


4. When JBOD's are used ?
“Just a Bunch of Disks”
It is a collection of disks that share a common connection to the server, but don’t include the mirroring,
striping, or parity facilities that RAID systems do, but these capabilities are available with host-based software.

5. Differentiate RAID & JBOD ?

RAID: “Redundant Array of Inexpensive Disks”
Fault-tolerant grouping of disks that server sees as a single disk volume
Combination of parity-checking, mirroring, striping
Self-contained, manageable unit of storage

JBOD: “Just a Bunch of Disks”
Drives independently attached to the I/O channel
Scaleable, but requires server to manage multiple volumes
Do not provide protection in case of drive failure

6. What is a HBA ?
Host bus adapters (HBAs) are needed to connect the server(host) to the storage.

SATA - Serial ATA Controllers Video Review


RAID (Redundant Array of Independendt Disks) Controller Review Video


7. What are the advantages of SAN ?

Massively extended scalability
Greatly enhanced device connectivity
Storage consolidation
LAN-free backup
Serverless (active-fabric) backup
Server clustering
Heterogeneous data sharing
Disaster recovery - Remote mirroring
While answering people do NOT portray clearly what they mean & what advantages each of them have, which are cost effective & which are to be used for the client's requirements.

Please focus on having your fundamentals STRONG & PERFECT.
Write to me roger.smithson@gmail.com to get more interview questions for storage jobs

storage area networking - real company interviews & jobs

SEND AN EMAIL TO roger.smithson@gmail.com & recieve a FREE FULL FEATURED SAN Tutorial Guide.pdf with more than 124 pages . Boost for a Career in Storage.
Index of all postings till date.
Virtual Tour of Cisco Production Data Center,San Jose,California

1.Job requirements for SAN/storage jobs
2. Your Resume completely improvised - See how I can help you boost your Resume
3. STRATEGY: Getting a High paying Storage JOB
4. Live SAN Company interview questions
5. Storage jobs interview questions & answers - Series 1
6. SAN jobs interview questions - Series 2
7. Storage job interview - How will be a Real Job Interview
8. What is Storage area network - Technical terms Explained
9. Regular day in a Storage Professionals Office Life
10. How can I get entry into a Storage Area Networking Job ?
11. Storage jobs Salary structure - How much they pay
12. Storage job questions - for a starter
13. SAN jobs or Storage Area Network Jobs - How You Can Get
14. Comments on Storage jobs blog are very much appreciated
15. Job Requirements & Expectations for Storage/SAN jobs

Cisco Catalyst switches and are they expensive

Cisco Catalyst 6500 Series switches & 3600 MultiService switches



See Next Images & Description in Next Page

Write to me roger.smithson@gmail.com & I can send u a detailed pdf on Cisco switches because they need huge PDF's to understand. I really appreciate the amount of time Cisco OCC(Operational Control Center) guys spend configuring, fixing ,troubleshooting these highly complex switches ,director level switches & routers.

SEND AN EMAIL TO roger.smithson@gmail.com & recieve a FREE FULL FEATURED SAN Tutorial Guide.pdf with more than 124 pages . Boost for a Career in Storage.

Storage Switches in Cisco Central Network Lab

Storage switches


Stacks of storage switches from Cisco which are used to monitor more than 5000 network nodes - network redundancy as well as high availability is built into these enterprise level storage switches

See Next Images & Description in Next Page

Data Center Real Cisco Virtual Tour : Modems

Enterprise Switches & Network Modem's



This is Cisco's Production Central Lab from where they connect & control ( Monitor as well as Manage) more than 40 data centers around the globe & these modems & network switches are the crucial links for this.

Index of all postings till date.
Virtual Tour of Cisco Production Data Center,San Jose,California

1.Job requirements for SAN/storage jobs
2. Your Resume completely improvised - See how I can help you boost your Resume
3. STRATEGY: Getting a High paying Storage JOB
4. Live SAN Company interview questions
5. Storage jobs interview questions & answers - Series 1
6. SAN jobs interview questions - Series 2
7. Storage job interview - How will be a Real Job Interview
8. What is Storage area network - Technical terms Explained
9. Regular day in a Storage Professionals Office Life
10. How can I get entry into a Storage Area Networking Job ?
11. Storage jobs Salary structure - How much they pay
12. Storage job questions - for a starter
13. SAN jobs or Storage Area Network Jobs - How You Can Get
14. Comments on Storage jobs blog are very much appreciated
15. Job Requirements & Expectations for Storage/SAN jobs