Giving servers the boot

New boot-from-SAN technologies offer automated server provisioning and other advanced management goodies.

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- (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 in Alexandria, Va. 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 $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."

Giving it a remote boot

Boot-from-SAN establishes virtual disks on the SAN and stores the server's boot image, operating system, system settings and applications there. The server boots from the boot image and is connected to the operating system-application-setting image in another virtual disk.

The boot process involves loading the operating system code from the SAN when the server is turned on. The system BIOS is loaded first from a boot image; it initializes the hardware and loads the operating system, checks the hardware setup and creates a copy of the operating system in server memory.

Boot images also can be cloned to accommodate the deployment of multiple servers, each of which has the same identity. For instance, an IT shop may have images on its SAN for Web servers, Microsoft Exchange or SQL servers waiting in queue for deployment. In this way, customers could create physical servers or servers virtualized with VMware or the open source Xen that can be provisioned from the SAN as necessary.

The problem with deploying a boot-from-SAN and LUN-cloning strategy for server provisioning is that it is a manual process that is often complicated to set up.

"With traditional LUN cloning, the user is required to use exactly the same hardware configuration or risk driver mismatches," says William Hurley, senior analyst for the Data Mobility Group.

Walters says Red Hat warned him off boot-from-SAN technology because of all the troubles that could ensue. "It claimed to support boot-from-SAN in no way, and told us all sorts of bad things would happen if we tried," he says.

Each server attaching to the SAN also needs its own boot image. N-Port ID Virtualization from Emulex lets several virtual servers share the same HBA and subsequently the same boot image. Microsoft says it also is working on software to let a non-virtualized blade or other server boot from a single image on the SAN.

Software and hardware from Brocade also make the process of creating and deploying server images easier and more automatic. Brocade's Tapestry ARM, a technology the company acquired last year when it bought Therrion Software, consists of hardware - the Tapestry ARM Appliance - and software - the Tapestry ARM Service Processor. Tapestry ARM integrates into existing Brocade Fibre Channel SAN environments.

"Tapestry ARM uses boot-from-SAN and LUN-cloning technology wrapped up in a server-based software package to make it easier to provision and move and reassign server-to-storage relationships," says Brian Garrett, an analyst with the Enterprise Strategy Group. "Storage arrays that support boot-from-SAN and LUN cloning are missing the server-based software, that is, the boot manager."

ARM provides the missing automated boot-from-SAN and server-provisioning piece. "In ARM, more than one host computer can boot from the image," Hurley says. "Traditional [pre-execution] boot is normally a one-to-one operation."

With ARM, each server boots to the same image, and the Tapestry ARM Service Processor software picks up the individual applications, operating systems and configuration settings for the server from images stored on the SAN. When a new server needs to be deployed, Tapestry ARM communicates with the Fibre Channel HBA in the server and tells it where to find its operating system and application data on the SAN. The ARM software automatically accommodates differences in server hardware, letting a server with a different hardware configuration be swapped in if a server fails.

"If a server fails, [ARM] can direct another server to the first server's LUNs," says Randy Kerns, an independent storage analyst.

The ARM system keeps a repository of images for each type of server. These images may be called on and configured from the Tapestry ARM management interface. Tapestry ARM uses Microsoft's VHD technology, which captures the operating system and applications for the virtual machine in a single file. Among those vendors licensing VHD are BMC Software, Fujitsu-Siemens, Network Appliance, Softricity, Virtual Iron, XenSource and Brocade, which includes it in Tapestry ARM.

But the real advantage of Tapestry ARM is that it automates server deployment and provisioning. Whereas boot-from-SAN and LUN cloning are manual processes, Tapestry ARM's management interface can automatically carve out virtual disks and assign servers to LUNs.

Matthew Deveny, architecture manager for Sutter Health in Sacramento, Calif., has beta tested Brocade's Tapestry ARM. "We are front-ending an application out to 41,000 employees. Deploying, managing and provisioning that environment can be extremely complicated for those machines. We believe it can save us a lot in overhead in provisioning resources and ultimately allow us to take drives out of our blade and other servers," he says.

Walters of the Public Broadcasting Service agrees. He says, "The time is finally right for boot-from-SAN."

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