NAS tutorial Network Attached storage is still a Good Storage Solution

What is NAS ?
A NAS device is a server that runs an operating system specifically designed for handling files (rather than block data). Network-attached storage is accessible directly on the local area network (LAN) through LAN protocols such as TCP/IP.
NAS components
NAS appliances serve files in heterogeneous environments. The result is efficient access to data, regardless of where you're located in the organization or which devices comprise the network. The following several components make a NAS efficient:
A dedicated server: Usually a thin server within the storage device, the server has its own network address and allows all of the computers on the network to access the storage device without involving a host server. So, to some extent, the network is completely circumvented. For example, when the network experiences outages, users can still access data through the NAS appliance without being affected by the status of the network.

A thin server is a server with just the basic software and hardware to perform a specific function.

A network connection: This is typically an Ethernet connection. The connection to the LAN or WAN allows access to data from all points on the network without consideration to where the user making the request actually resides on the network.

Software: This provides a range of services. The most typical of those services are access to storage, storage I/O (input/output) processing applications, RAID (redundant array of independent disks) storage control, security, administration, and monitoring.

A NAS appliance is connected directly to a network and provides file-level access to data using standard data access protocols. The data stored in a NAS appliance is accessible to users across the organization, as well as to application servers, and remote servers that have access to the network. The file system the NAS appliance uses is determined by the location of the data that is requested by the application client and whether it's in a cache or in storage.

For complete efficiency, the NAS appliance usually occupies its own node on the network. In such a configuration, the single appliance (server) handles all the data storage on the network, taking the load off of the application or enterprise server. This provides a high level of file consolidation, streamlines file access, and lowers the cost of managing storage.

Additional reductions in cost can be found in the fewer pieces of hardware required. With fewer devices to manage, fewer problems occur, even when multiple NAS appliances are needed to accomplish efficient storage.

In future posts you'll find out how to determine whether you need a single NAS appliance or multiple NAS appliances to meet your storage needs.

NAS hardware and software

NAS hardware is fairly straightforward. The NAS device is a self-contained, Plug and Play unit that connects directly to the network and, in most cases, can be installed and configured in 15 minutes or less. That ease of installation is the answer to every busy IT manager's prayers. However, there are other advantages to NAS, such as the following:

High availability: Many NAS appliances have fault-tolerance capabilities or clustering functionality built in.

Scalability: NAS appliances scale easily in both capacity and performance.

Universal connectivity: NAS appliances typically allow for multiple network connections. This enables more users to connect to a common storage element at any given time.

Data sharing: One of the most basic functions of NAS is heterogeneous data sharing via the built-in file-sharing capabilities.

Storage management: NAS storage management is centralized and the administration of system management is simple. One advantage of this simplified management is the increase in capacity that can be managed by each administrator.

Most NAS devices also have a set of core software features that power the solutions. Those core features are the operating system, management capabilities, and universal connectivity, and although the specifics of these core features differ according to vendor, a basic set of core features comes packaged with most NAS appliances.
Operating system

The operating system is preinstalled on the NAS appliance and can affect how the device is deployed. The three most common operating systems are Microsoft Windows Storage Server 2003, Unix/Linux, and NetWare. The operating system that you select depends on your organization's preferences and business needs.
Management capabilities

Most NAS appliances have preinstalled management capabilities, usually accessible via a web browser. These management features mean that managing NAS is flexible and can be accomplished from any location with web access.
Universal connectivity

One of the most attractive features of NAS is the ability to access files using a variety of disparate file protocols. This ability means that you don't need to acquire any additional seat licenses, and each different existing server (or even multiple servers with different operating systems) doesn't need its own storage box.
Additional software features

In addition to the core software features of NAS devices, most vendors also offer a variety of advanced, value-added software capabilities. These capabilities are pick and choose, according to the specific needs of your business. It's in the pick-and-choose features that you begin to differentiate the low-end NAS installation from the mid-grade and high-end NAS installations. Your specific business needs and vendor offerings determine which advanced software features are appropriate, but some of the extended features are:

Server clustering: In some cases, you want to configure your storage solution to include more than one NAS appliance, but you want all of the NAS appliances to act as one unit. Server clustering is the capability that enables this feature. You should consider using server clustering if high availability is required. If your data is mission critical, or if having a temporary outage of your organization's NAS appliance could stop the normal workflow of your business, multiple NAS devices and server clustering are combined to create a redundant solution that assures you'll never have downtime. When clustered, if one NAS device fails, other NAS devices in the cluster pick up the slack.

Data replication: This is a protection technology that creates a complete mirror image of all the data located on one NAS appliance to a second NAS appliance. After the initial mirroring is completed, only the changes to the data are synchronized at the time of the change. If a network failure or outage occurs and data needs to be restored quickly, an exact, easy-to-access replica of that data already exists.

Data snapshot: Occasionally, a user accidentally deletes a file and, in some cases, the IT department (or IT person, as the case may be) has to be called in to recover the deleted data. This situation can be time-consuming, frustrating, and costly. However, having the ability to take a data snapshot mitigates that expenditure. A data snapshot is a point-in-time copy of all data on a NAS device that is duplicated and stored on another NAS device or other backup media. The snapshot can then be accessed from individual workstations as needed, without getting IT involved.

A NAS solution is pretty straightforward, and that's one of the reasons that it's one of the fastest-growing storage technologies in the United States at this time. However, there are instances in which a single NAS appliance won't do the job.

How To Setup Storage Lab : Simple & Cheap

Motivated by Sarfaraz's comment for this blog asking for a post about Setting up a Scaled down(Home version/Cheap) Storage Lab,here is a an article on the same topic.

NAS ( Network Attached Storage)

Below is a Video of a simple NAS which you can build buying an old IDE hard disk drive along with some equipment like Vantec Nexstar LX NAS.
It looks like an external hard drive(USB based) but this same device can be connected thu Network cable & will actually become a simple NAS device.


FreeNAS.org - Below is a Video detailing how a NAS can be build using software from freenas.org & using an old PC with some hard disks. This video is quite interesting but the NAS topic starts somewhere in the middle - so be patient & its a huge video file.


BELOW IS THE MOST INTERESTING STORY
Skyers is more than happy to share the saga of building a FC SAN(Fibre Channel - Storage Area Network) at home. The SAN was entirely 1 gigabit per second (Gbps), and all the disks were SCSI(Small Computer System Interface). Skyers said he got most of the half-terabyte system in parts on eBay.

"It's actually funny how cheap these parts are," Skyers said; for example, his FC-connected SCSI array cost $22 on the online auction site. An old Compaq 1 Gbps FC card cost him $4. A newer QLogic FC card was more pricey, at $700, but the complete system, he said, including processors, memory, RAID controllers, and IDE and SATA disks -- tiered storage in the home -- set him back around $5,000.

"I guess I'm obsessive-compulsive in a way," he said. "I need to know as much about what I work with as possible. I can't take it apart and test the limits, much less break stuff, at work."

The initial push, he said, was to learn about FC signaling, how fast it can go, and how to get performance numbers from it. "I didn't want to just read the information off someone's marketing media," Skyers said.

One thing Skyers said he learned quickly about FC was that compatibility issues between different cards can be frustrating.

"They're both running the same protocol," Skyers said. "I don't get why one slightly newer card won't work with the older one."

Wrestling with the FC SAN -- contrasted with the rest of his Ethernet home network and the advent of new high-capacity NAS boxes like Buffalo Technology's new Drivestation Duo, which packs 1 TB of storage into a $500 product -- has made him convinced FC will soon be a thing of the past at work as well as at home. In the enterprise space, Skyers said, he compares Sun Microsystems Inc.'s "Thumper" 24 TB DAS array to the Buffalo box. "If I can have a subsystem in a box like that that's the size of something like Nexsan's ATABeast with about a gazillion drives, and I can hook it up to my IP switch, throw one in another place for disaster recovery (DR), what do I need a SAN for?" he said.

Meanwhile, Skyers said, his home experiments have only deepened his love for VMware, another key component, he said, in consolidating down into a box like Buffalo's. However, he said, through experimentation he has learned that VMware is "very picky" about installing on a SCSI drive in the physical host. "I tried a Linux trick to present a SATA and an IDE drive to it as a SCSI disk, but no dice," Skyers said.

What's next? DR and exploring the WAN -- echoing enterprise trends. "A cousin in Florida and I are going to set up separate islands of storage several hundred miles apart, and then see if we can replicate back and forth to them over low-bandwidth connections," Skyers said.

Frustration with data management -- at work and at home

Jeff Boles, IT manager for the City of Mesa, Ariz., says he thinks home storage is a "canary in the mine" for the enterprise. "What you see at home today will become active in the enterprise tomorrow."

Boles said he uses a NAS device and open-source software Debian for management. He boots the NAS device from a flash drive and mirrors it to another identical box. The clients that connect to it are a variety of laptops.

The problem he wrestles with, Boles said, is similar to one being articulated in the enterprise today -- data management and classification. Boles, an avid photographer, stores around 40 gigabytes (GB) of digital photos at any one time, as well as various versions of those photos that have been touched up. "There's a pressing need there to be able to correlate versions of the same file," he said. "There's really no good versioning system -- and it's made data proliferate. My biggest beef with storage in general, at work and at home, is the absurd gap between how data is structured and how it's physically stored."

Hope you have some idea now on how to setup ur own Storage lab - if anyone of u does some experiments plz do email me & I'll be happy to share with all our readers.

Email ur friends about this blog & CC me roger.smithson@gmail.com . I Will send u links of Storage or Tech Job Video with lots of Real Industry Exposure for every friend you email. I want to spread the word & help more people thru this blog .U'll also get many more Surprise Gifts to Boost your Career & Salary.

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DEFINITIONS OF TERMS USED ALL THROUGHOUT THIS BLOG

A node is a computer attached to a SAN.
A SAN is a high-speed subnetwork of shared storage devices.
Software that manages San file system functions, such as file locking, space allocation, and data access authorization, is called the Metadata controller.(This is an Apple Storage implementation term - other companies use other terms)
Metadata controller uses callbacks to communicate with file system clients.

Xsan file system client software runs on all nodes in the SAN and communicates with the metadata controller in order to provide Xsan services. The term file system client refers to a node that is running the Xsan file system client software.

A redundant array of independent disks (RAID) device is a category of disk devices that combines two or more drives increased for fault tolerance and performance. There are several RAID levels:
*Level 0 provides data striping, where blocks of a file are spread across multiple disks, increasing performance; this level does not have any provisions that increase fault tolerance.
*Level 1 provides disk mirroring.
*Level 3 provides the data striping of Level 0 and also reserves a disk for storing error correction data, thereby increasing performance and fault tolerance.
*Level 5 provides data striping at the byte level and maintains stripe error correction information.

A JBOD (just a bunch of disks) is a disk that is not configured for RAID.

A logical unit number (LUN) is an aggregation of physical devices. Applications access LUNs through the special files in the system’s /dev/disk directory. For RAID devices, a LUN is typically a RAID-5 with three or more physical drives making up the LUN. For JBOD devices, one JBOD is one LUN.

A storage pool is a grouping of LUNs that have the same characteristics. Another term for storage pool is stripe group. One or more storage pools form a mountable volume. The number of volumes hosted by a single Xsan metadata controller should not exceed eight.

Stripe depth is the number of disks that have been assigned to a storage pool.

The stripe breadth is the maximum amount of data that is read or written before switching to the next LUN in the storage pool. When the last LUN is reached, I/O operations go back to t he first LUN. This is how large logical I/O operations are broken down into stripes across multiple LUNs. For example, if the stripe breadth for a storage pool is set at 4 MB, each I/O operation on that storage pool is physically no more than 4 MB. A 16 MB I/O operation would be broken down into 4 physical I/O operations.

A stripe line is the stripe breadth multiplied by the number of LUNs in the storage pool. To maximize performance, make I/O requests that area stripe line in size.

For real-time I/O, well-formed I/O is I/O that is a stripe line in size. This size makes the best utilization of the disks in the storage pool and maximizes the transfer rate. For non-real-time I/O, well-formed I/O is I/O that is memory aligned (modulus 4 bytes), 512-byte sector aligned, and modulus sector sized.

A block is the smallest number of bytes that can be read or written.

Storage pools can be assigned one or more values, known as an affinity identifiers, and a file can be assigned one affinity. When a request is made to allocate space in a file for which the affinity has been set, the space is allocated from the storage pool that an affinity identifier that matches the file’s affinity. For example, consider a SAN with some moderate performance JBOD LUNs and some high performance RAID-5 LUNs. By grouping the RAID-5 LUNs into the same storage pool and assigning them a specific affinity identifier, the developer can steer performance critical data to that storage pool. Files containing less critical data or files that do not have an affinity are assigned to the storage pool that consists of JBOD LUNs.

When a storage pool is in real-time I/O mode, file system clients that have processes that do non-real-time I/O must request a non-real-time I/O token Xsan throttles the speed of I/O of applications that are not in real-time mode so that their I/O does not interfere with real-time I/O. This document uses the term gate to describe processes or file descriptors that are not in real-time I/O mode and the term ungated to describe processes or file descriptors that are in real-time I/O mode.

An extent is a chunk of file data whose allocation is contiguous on a storage pool. A file’s data may be stored in one or more extents. Information about an extent includes its file-relative starting byte offset, its file system starting byte offset, the file system ending byte offset, and the ordinal of the storage pool on which the extent resides. File system clients use extent mapping tables to load information about a file’s extents. Loading extent information improves performance by eliminating a subsequent trip by the file system client to the metadata controller in order to retrieve extent information for the range mapped by an I/O request.

When there are two or more storage pools that have the same characteristics, an allocation strategy is needed. The strategy can be to round-robin files through the set of storage pools, balance the remaining space in the storage pools, or fill the first storage pool before going to the next storage pool.

A disk file system, such as a UFS or HFS+ file system, resides on the internal drives of a computer or on storage devices that are attached directly to the computer. A network file system allows data on internal drives or on directly attached drives to be shared with other computers on the network. Examples of network file systems include Apple Filing Protocol (AFP), Server Message Block (SMB), Common Internet File System (CIFS), or Network File System (NFS). A distributed file system is a blend of disk file system and network file system used to simplify data sharing through the creation of a single shared name space across a collection of servers. A cluster file system gives multiple computers simultaneous, very high-speed access to all shared data residing on an external, centralized storage pool. The storage pool typically consists of highly available RAID systems. Xsan is a cluster file system

SAN Architecture


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