Is It Time to Dump Your Disks?

With the proliferation of inexpensive iSCSI targets entering the market and more diskless options becoming available for Windows, now is a cost-efficient time to consider moving to diskless clients and servers.

eWEEK Labs believes there are several areas where it makes sense for IT departments to consider migrating boot images off internal drives and onto external storage. The most obvious place for diskless clients is the blade server market, since removing hard drives from a server blade not only reduces power consumption but also lowers the amount of heat within the blade server chassis.

Servers and workstations are also good candidates for diskless workstations. Products such as EqualLogic Inc.s EqualLogic PS200E bring snapshot capabilities to the iSCSI space, allowing IT managers to quickly get corrupted workstations or servers back online by simply restoring an older image of the operating system disk. Diskless client implementations centralize data onto the SAN (storage area network), which means IT staff members no longer have to spend hours rebuilding systems when operating system drives go down.

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Fibre Channel HBAs (host bus adapters) can provide diskless client capabilities. In the diskless Fibre Channel HBA scenario, when a server powers up, the HBAs BIOS logs in to the SAN fabric and directs the server to the storage array that houses its operating systems and applications. With Fibre Channel HBAs running at 1G bps to 2G bps, the SAN shouldnt be a bottleneck for server performance.

When you combine the expense of Fibre Channel HBAs, switches, cabling and storage, deep pockets are clearly necessary to convert a data center to diskless booting using a Fibre Channel SAN. It makes the most fiscal sense to implement Fibre Channel diskless systems on midsize or large servers because those servers are likely to already have SAN connectivity for accessing networked storage.

iSCSI HBAs from vendors including QLogic Corp. provide diskless boot capabilities at a lower entry cost, with prices starting at about $300 per card, compared with $500 per card for Fibre Channel. Like a Fibre Channel HBA, an iSCSI HBA is activated when a server is in the post state; the HBA locates the external device from which the server can get its boot image.

iSCSI HBAs save money because they can run on standard IP networks, which are found in most IT shops. (Gigabit Ethernet is recommended.)

Software-based iSCSI initiators from EmBoot Inc. and others are now available to make the implementation of diskless clients even less expensive.

EmBoots NetBoot/I software, released in June, uses DHCP (Dynamic Host Configuration Protocol), PXE (Preboot Execution Environment) and TFTP (Trivial File Transfer Protocol) to connect the server to the iSCSI SAN and direct it to the right boot image, without the use of specialized HBAs. NetBoot/I is priced starting at about $85 per client.

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