BY HEIDI BIGGAR
Recent product news out of Compaq and Hewlett-Packard has sparked some interesting discussion not only about the two companies' virtualization plans, but about the eventual role that various virtualization levels-server, fabric, and storage system-will ultimately play in end users' storage environments.
"The question is why anyone would want, or need, to have all three virtualization capabilities," says John Webster, senior analyst with Illuminata, a consulting and research firm in Nashua, NH. "If you've got virtualization at the SAN [storage area network] fabric level, why would you also need virtualization at the array level? Or, perhaps more importantly, how would you reconcile the two?"
Compaq officials, for example, believe the three levels can be used together or independently for maximum user benefit. Of course, at the other end of the spectrum, others argue the contrary.
The solution, says Dan Tanner, a senior analyst with the Aberdeen Group consulting firm, in Boston, may be a storage virtualization standard, which would allow various virtualization elements to interoperate. "Standards could make virtualization a win for everyone-administrators, suppliers, and users," explains Tanner in a recent Aberdeen InSight report. (For more information, check out www.aberdeen.com and "Storage virtualization needs standards," InfoStor, November 2001, p. 58.)
"Software from multiple vendors-of host computers, storage subsystems, and virtualization engines-would work cooperatively by passing standards among one another," says Tanner.
For Compaq and HP-both of which announced products with virtualization elements at the recent Storage Networking World (SNW) show-the ability to reconcile their respective virtualization capabilities may prove critical, especially if the two companies merge.
"If it's just Compaq, you've got to reconcile EVA [Enterprise Virtual Array] with Compaq's out-of-band virtualization capability. Spin StorageApps into this, and you may have a mess," says Illuminata's Webster. (Hewlett-Packard acquired virtualization vendor StorageApps earlier this year.)
At SNW, Compaq and HP each announced virtualization "firsts." Compaq launched its EVA array, the company's first true high-end disk array, as well as the first Compaq device to integrate elements of the company's highly anticipated VersaStor virtualization technology.
VersaStor is Compaq's umbrella term for its over-arching virtualization strategy. Basically, EVA provides virtualization at the storage system, or disk-array, level, explains Mark Lewis, vice president and general manager of Compaq's Enterprise Storage Group. "For very large companies, we will build VersaStor in to the SAN."
Compaq last month reported increased vendor support for a SAN-wide VersaStor capability. For example, Emulex, JNI, McData, QLogic, StoreAge, and Troika signed letters of intent to develop "VersaStor-ready" products. Brocade also announced support for the technology.
For now, however, Compaq is limited to doing virtualization at the storage system level. According to Lewis, the benefits of this type of implementation are more-efficient use of storage capacity, simplified management, and lower storage-related costs. Compaq achieves this through a mix of disk virtualization, Virtual RAID (or Vraid), virtual snapshots, and virtual data cloning capabilities. All three are enabled by VersaStor technology.
- Vraid-The EVA supports multiple virtual disks of varying capacity and RAID types within a single storage pool. All virtual disks in a pool spread their capacity across all the physical disks that contribute to that pool. For example, instead of assigning two disks to a RAID-1 configuration, data can be spread across multiple disks, which can significantly improve performance.
Additionally, EVA has an on-the-fly leveling algorithm, which redistributes a virtual disk's blocks evenly across as many spindles as the virtual disk's redundancy type will allow. Users determine what level of protection they want.
- Virtual snapshots-Unlike standard approaches, which pre-allocate space for snapshots, the EVA allocates space as needed for incremental changes. The snapshot volume, or Vsnap, provides virtually capacity-free, point-in-time copies. These snapshots are taken in seconds and can be archived to disk for fast recovery. This technology allows the virtual capacity of the EVA to exceed its physical capacity.
- Virtual data cloning-Similar to traditional cloning techniques, EVA's Virtually Instantaneous Snap clone makes a complete copy of the original data. Where EVA differs is in its ability to allow users to access the original virtual disk while the cloning process is in progress. This gives users near-instantaneous point-in-time clones of virtual disks.
Other EVA features include 2Gbps Fibre Channel connectivity with up to 200MBps bandwidth per path, and up to 12TB of capacity with 168 disks or 17TB of capacity with 240 disks per controller pair. Lewis claims that the array is up to 8x faster than Compaq's previous highest-performing system.
Analysts say EVA will compete on two levels. "On one hand, it could effectively compete against EMC Symmetrix, IBM Shark, and Hitachi Data Systems' arrays in the open-systems market," says Randy Kerns, a partner at the Evaluator Group consulting/research firm, in Greenwood Village, CO. "But it could also go up against HP's Virtual Array and StorageTek's Shared Virtual Array," he says.
Meanwhile, Hewlett-Packard at SNW detailed plans for an entry-level to mid-range storage system. The bundled SAN configuration, code-named SAVA, is due out early next year and is the first HP product to integrate HP virtual arrays, Netservers, and Fibre Channel host bus adapters with SANLink virtualization software from StorageApps (see diagram). In September, HP completed its acquisition of Bridgewater, NJ-based StorageApps in a stock-for-stock transaction valued at $350 million.
HP says it will price SAVA under $100,000 to reach a broad range of users. "With SAVA, HP is trying to appeal to end users that wouldn't typically install a SAN," explains Kerns. "This is a very large market-much bigger than the [traditional] SAN segment."
"SAVA is the next turn of the crank for us," says Brice Clark, HP's director of strategy for network infrastructure solutions and data-center networking. "It has advanced virtualization, security, snapshot, and remote-mirroring capabilities." Additionally, the SANLink virtualization software works with storage arrays from Dell, EMC, Hitachi, and LSI.