Storage Area Networking SAN NAS Fibre Channel iSCSI

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Thursday, January 25, 2007

iSCSI Storage Solutions to solve Business Requirements

Continuing the previous post on iSCSI . This is an important topic for Storage professionals as its going to be the next major trend.

Adaptec iSCSI initiator


iSCSI host bus adapters (HBAs) are network interface controllers that incorporate a TCP Offload Engine with onboard iSCSI processing. iSCSI HBAs are usually abstracted purely as SCSI controllers by the operating system driver system. In this case, the HBA is not a part of the system network stack. Recently there has been considerable effort in providing standard vendor-independent iSCSI management facilities via operating system driver interfaces. These standard interfaces also work with software initiators.

Qlogic iSCSI HBA

Since iSCSI HBAs offload considerable processing in the iSCSI stack, interrupt generation is less than comparable software initiator setups. Applications leaving few spare CPU cycles should benefit from the use of a dedicated HBA.

HP Fires a Bullet through its Storage array for a Stress Test


iSCSI HBAs have the advantage of including PCI option ROMS to allow booting from iSCSI targets. Alternative iSCSI boot methods with software initiators would require substantial work.

The following vendors have developed iSCSI HBAs:

* Adaptec (Product is discontinued.)
* Alacritech
* Intel (Product is discontinued.)
* Qlogic
* Silverback Systems External Link

Targets
Most industry focus has been placed on creating iSCSI disk targets though iSCSI tape and medium changer targets are popular as well. So far, physical devices have not featured native iSCSI interfaces on a component level. Instead, devices with SCSI Parallel Interface or Fibre Channel interfaces are bridged by using iSCSI target software, external bridges, or controllers internal to the device enclosure.

Alternatively, disk and tape targets can be virtualizations. Rather than representing an actual physical device, an emulated virtual device is presented. The underlying implementation can deviate drastically from the presented target as is done with Virtual Tape Library (VTL) solutions. VTLs use disk storage for storing data written to virtual tapes. As with actual physical devices, virtual targets are presented by using iSCSI target software, external bridges, or controllers internal to the device enclosure.

Addressing and Name formats
iSCSI provides two name formats for different types of naming authorities:

* iSCSI Qualified Name (IQN), Format: iqn.yyyy-mm.{reversed domain name} (e.g. iqn.2001-04.com.acme:storage.tape.sys1.xyz)
* Extended Unique Identifier (EUI), Format: eui.{EUI-64 bit address} (e.g. eui.02004567A425678D)

In the case of IQN the address is qualified by a date (yyyy-mm) since a domain name can expire or be acquired by another entity. EUI is provided by the IEEE Registration authority in accordance with EUI-64 standard.

Each target is defined by three or four fields:
HostNameOrAddress PortNumber iSCSIName CHAPSecret (optional)

Example:
iscsi.fake.com 3260 iqn.2003-01.com.ibm:00.fcd0ab21.shark128 "123ismysecretpassword"

Storage Area Network and Network Attached Storage

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