If Dell Inc. had its way, Massachusetts Institute of Technology (MIT) Medical -- already a Dell shop for servers and DAS -- would now be using the AX 100 Clariion, a low-end array Dell resells from EMC Corp. But according to MIT applications and technology specialist David Forristall, a SAN from Compellent Technologies Inc. caught his eye instead.
Forristall said that the primary distinguishing feature of Compellent's Storage Center SAN product is the way it virtualizes data at the block level, striping data from all applications across all of its disks and presenting the user with one storage pool.
"It was an important differentiator from the Clariion," Forristall said. "We don't have to take individual disks and assign them to a volume -- we just get one chunk of space," making it easy to provision storage.
"If we had a hardware failure, it would be easier just to detach and replace the server, and leave the data to live on the SAN," he said. "The Dell technical representative said it could be done with Clariion but recommended against it."
According to Forristall, Compellent's scaling model also appealed to him.
"With the Clariion, it would max out at four servers, and then you had to go up to the next tier," he said. "With the Compellent, the entry-level pricing maxed out at eight servers -- so we wouldn't move up pricing tiers as fast."
Today, MIT Medical is running a 3.2 terabyte (TB) Storage Center SAN, which is currently storing 1.7 TB of data from 30 Dell PowerEdge servers. The servers run administrative file systems, a SQL database and an electronic medical records (EMR) application from AllScripts LLC on NetWare and Windows Server 2003. Compellent doesn't sell its products directly, so MIT Medical purchased the Storage Center SAN from Boston-area reseller Winslow Technology Group.
It might seem worrisome to have every disk in an array storing pieces of data from every application, but Forristall said he had also put Compellent's failover mechanism into action when a disk failed three months ago and hadn't lost any data.
Forristall said the storage controller had kept track of what data is stored on which physical disk and reserved two of the 16 Fibre Channel disks inside the array as "hot spares." When the disk failed, he said, the controller rewrote the data to one of the spares and replaced the failed disk with it, while Compellent's technical services sent over a new disk to replace the hot spare.
"Winslow services had a new disk to us in under an hour," Forristall said.
For backup, the Storage Center SAN takes snapshots and stores them in a partition on the SAN and on a separate Dell server, which in turn writes copies to a 400 GB portable Universal Serial Bus drive. MIT Medical also backs up its data to the school's main data center across campus for disaster recovery, although Forristall said he was considering using Compellent's remote replication feature -- dubbed "Remote Data Instant Replay" -- to do his own off-site storage.
Though he's pleased with the Compellent product, Forristall admitted he didn't have much to compare it to besides the AX 100 -- or much experience with networked storage in general. MIT Medical had only switched away from DAS on the advice of its EMR software vendor, and Forristall said he and his colleagues had been somewhat intimidated by SANs.
"We'd seen midrange SANs demonstrated at trade shows," he said. "But it was new to me and the other guys I worked with. We couldn't always wrap our heads around it.
"It seemed easy to use in the demos we had," he said of the Compellent product. "It was my understanding from other people in the industry that not all SANs are that way."
An EMC spokesperson deferred to Dell for a response to MIT Medical's comparison of Compellent with the AX 100; Dell's representative declined to comment.
Compellent's product falls into the midrange SAN bracket, a hotly contested market overflowing with vendors, including all the major players as well as EqualLogic Inc., Intransa Inc., LeftHand Networks Inc., Xiotech Corp., 3Par Data Inc. and Pilar Data Systems Inc.