Giving servers the boot

In response to IT demands for increased efficiency in managing diskless and blade servers, storage-area network vendors have begun crafting next-generation tools that perform advanced server provisioning. Tools such as Brocade's Tapestry Application Resource Manager, Microsoft's Virtual Hard Disk or Emulex's N-Port ID Virtualization are proving much easier to use than predecessors such as boot-from-SAN and logical-unit-number cloning.

While long enabling SAN-based provisioning of servers and storage, boot-from-SAN (in which servers boot from volumes on the SAN) and logical unit number (LUN) cloning (the copying of data from one virtual disk to another) have been difficult to implement. The new generation of tools, which offer better provisioning capabilities and support for a wider range of storage options, are a boon for IT shops focused on building New Data Center infrastructures. They offer such advantages as the ability to consolidate resources by deploying diskless and virtualized servers and to centralize management. With these tools, IT can store server images (including applications, operating systems, settings and data) on the SAN and administer and parse them out from a single location.

Recovering servers quickly may be the greatest advantage of boot-from-SAN and SAN-based provisioning. If a server fails, IT can easily deploy a new one using the server image on the SAN. That process takes less time than configuring a new server. Likewise, dozens of Web servers can be created with a single click of a button once their identity - the image - has been created. Rather than reinstalling the operating system, applications and configuration settings and a copy of the data from a backup tape, IT simply drops the new server into the network and configures it to use the boot and application and operating system image stored on the SAN.

Michael Passe, storage architect for CareGroup Healthcare System's Beth Israel Deaconess Medical Center in Boston, is considering boot-from-SAN and server and storage provisioning for those reasons. "We are talking about boot-from-SAN specifically to aid in disaster recovery, since we could clone and replicate the system volumes for many systems," Passe says.

Of boots and blades

The technology behind boot-from-SAN is nothing new. In the late 1980s, diskless workstations equipped with a boot ROM picked up their identities from the file server. Unix workstations have booted from the network since the days of Digital Equipment. However, today's boot-from-SAN technology supports automated provisioning of server resources, which eases the deployment of diskless servers and blades, users say.

"I hope to get to boot-from-SAN later this summer in our IBM BladeCenter servers," says Ken Walters, senior director of enterprise technology for the Public Broadcasting Service. Over the last couple of years, the company has been using the blade servers and running VMware's ESX Server for consolidation, he adds.

ESX Server provides boot-from-SAN because servers are being booted off virtualized SAN disks, Walters says. What he really needs, he says, is to boot blades off iSCSI SAN disks. While Adaptec and QLogic make specialized host bus adapters (HBA) that let users boot their blades from IBM BladeCenter computers, these hardware-based iSCSI HBAs can be expensive, topping out at about US$700 apiece. Instead, Walters hopes to use Microsoft's and IBM's software-based iSCSI boot, expected to be available later this summer.

When implemented in the server Basic Input/Output System (BIOS) or in HBA firmware, the iSCSI Software Enabled SAN boot lets BladeCenters and other diskless servers connect to and boot from the iSCSI SAN. Using this software, Walters will boot his blade servers from StoneFly's iSCSI-based Storage Concentrator, which attaches to inexpensive advanced technology attachment or Serial Advanced Technology Attachment drives. Among the partners signed on to support this software-based boot are Dell, emBoot, Intel and QLogic, as well as iSCSI vendors Alacritech, EqualLogic, FalconStor, Intransa, LeftHand Networks, Nimbus Data Systems and SANRad.

From Walters' point of view, the most compelling reason for booting off the SAN is to improve storage consolidation. "I added up all the direct-attached storage I had and discovered that I had almost as much unused disk space in all these disks as I did on my SAN."

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