POWER SOLUTIONS

STORAGE TECHNOLOGYbenefits including enhanced disaster tolerance, centralized administration,minimized cost of ownership, high-availability storage,enhanced business continuance, rapid server repurposing, and imagemanagement consolidation.Enhanced disaster tolerance. If a server becomes faulty,unavailable, or compromised in a boot-from-SAN environment,it can be swapped out for a replacement server with the sameconfiguration right away. This approach enables administratorsto deploy the replacement server without first being required toreconstruct the booting, operating, and application environments.Administrators do not have to swap out hard drives, reconfigurearrays, or restore data and applications from backup—saving valuabletime during a mission-critical restore. The capability to replaceand add servers in minutes can enhance return on investment(ROI) by helping to prevent lengthy downtime of core servers—alsohelping enterprises to avoid service interruptions in the missioncriticalapplications that run on those servers.Centralized administration. Transitioning from a distributedserver environment, where the boot device is local to the server,to one or more storage arrays on a SAN helps reduce the managementoverhead associated with traditional distributed environments.Centralized systems management can streamline administrativeworkflow and typically requires fewer administrators to maintainthe environment.Minimized cost of ownership. Booting from a SAN enablesthe deployment of diskless servers. Depending on the networktopology and number of servers, organizations can gain significantsavings by using diskless servers. For example, 100 servers accessingredundant 250 GB drives can share a single storage array, using afraction of the number of disks that would be required to supportthe same number of servers if each server were equipped with itsown local disk storage.High-availability storage. Booting from a SAN usually involvesbooting from an external RAID controller. Typically, external RAIDcontrollers enable high availability. Adding the multipathing featuresof a Fibre Channel host bus adapter (HBA), which is required whenbooting from a SAN, helps provide even higher availability throughredundancy. This benefit also enhances ROI because RAID controllercosts can be amortized over multiple servers.Enhanced business continuance. Data protection featuresinherent in SANs—such as backup and restore, data migration, datareplication, and disk-capacity expansion features—can be effectivelyused for the boot drive on the RAID controller without incurringadditional cost.Rapid server repurposing. By storing the boot image on aSAN, administrators can create an application instance that includesthe logical grouping and associations of a server model, installedapplications, the OS image, the actual boot logical unit (LUN), andthe data LUNs. A preconfigured application instance can be used torapidly repurpose a server to perform a specific job at a scheduledtime (for example, a backup server) or dynamically repurpose theserver to sustain the workload of a specific job (for example, a databaseserver). This instance can also be used for disaster recoveryto quickly replace a failed server.Image management consolidation. Storing boot images ona SAN enables consolidation of homogeneous boot images on thesame LUN in the RAID unit, as well as consolidation of incrementalchanges on a snapshot LUN.Choosing applications that are well suitedto boot from SANsApplications that require high data availability are good candidatesfor boot-from-SAN implementations. Examples of such applicationsinclude but are not limited to:• Microsoft ® Exchange servers as well as database, e-mail, andWeb servers located in data centers or server farms• Commerce servers that handle revenue-critical applications• Enterprise servers that provide access to critical networkresources and services• Blade server installations, in which small servers built on cardsplug into stackable racks that offer shared power supplies andnetworking capabilities, allowing administrators to add serversquickly and cost-effectively on an as-needed basisDefining boot-from-SAN standardsToday, no standards are associated with booting from SANs—either programmatically or in best practices. However, the StorageNetworking Industry Association (SNIA) has formed a Host TechnicalWorking Group (TWG) to address the needs and technological challengesassociated with booting from SANs. These standards groupsare dedicated to help minimize costs and maximize interoperabilityof boot-from-SAN environments. Dell and Sun Microsystemsare co-chairs of the Host TWG; other active participants includeHP, Adaptec, Engenio, AppIQ, and VERITAS. The SNIA Host TWGfocuses on host-side storage management and is responsible forgenerating Common Information Model (CIM) profiles and subprofilesthat address storage resources associated with the host, whichinclude boot-from-SAN implementations.Currently, vendors must provide systems management functionalityto manage disks, RAID, enclosures, and boot methodologies. Thisadds complexity to systems management, especially in heterogeneousenvironments—which can increase the likelihood of errors and theconsequent financial burden on a data center that must safeguardagainst and recover from errors that may occur in a complex heterogeneousenvironment. Standardized boot-from-SAN practices canhelp streamline systems management and help administrators avoidcommon problems associated with such configurations.84DELL POWER SOLUTIONS Reprinted from Dell Power Solutions, August 2005. Copyright © 2005 Dell Inc. All rights reserved. August 2005