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Nexsan disk array combines SAS with MAID

Beth Pariseau, Senior News Writer

With the release of its SASBoy disk array, Nexsan Technologies is combining two technologies rarely seen together: high-performance SAS disks and spin-down for power savings.

SASBoy, Nexsan's first SAS disk array, contains 4.2 TB of 300 GB 15,000 rpm SAS drives, 4 Gbps Fibre Channel or 1 Gbps Ethernet ports, and up to 4 GB of cache. The array also has the ability to spin-down disks for power savings using Nexsan's AutoMAID feature.

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With this product, we're focused on fast random access of fixed-content storage.
Bob Woolery
marketing vice presidentNexsan
With the combination of SAS disks and spin-down, Nexsan is trying to fill a gap between Tier 1 transaction processing storage and bulk SATA secondary storage. "With this product, we're focused on fast random access of fixed-content storage," said Bob Woolery, Nexsan marketing vice president. One example of how this hybrid storage tier could be used would be to store the index of an otherwise static archive for fast search.

MAID was originally developed to prolong the lives of low-cost SATA drives, which have a lower MTBF than typical enterprise drives. But some industry observers aren't sure how much of a market exists for MAID on high-performance drives and the new type of storage tier Nexsan targets. "This is an unusual implementation of SAS," said analyst Arun Taneja, Taneja Group. "Right now it's hard to tell how customers will use it - but customers often find different creative ways to use systems."

Joe Funaro, director of technology for IT at US-based Lenox Hill Radiology, Diagnostic Radiology Associates and Park West Radiology, said he's already ordered his first SASBoy and will probably add more as he refreshes each of his data centres. The clinics are owned and operated by one management group, but each has its own IT infrastructure.

Funaro will use his first SASBoy for the primary SAN at Park West, attached to a PACS running on an IBM BladeCenter chassis and connected through iSCSI. Within six months, Funaro said he plans to add a Nexsan Assureon disk-based archive appliance at the Park West location and may duplicate that same configuration of BladeCenters, low-power switches, SASBoy storage and Assureon at all three data centres. At Lenox Hill's facility, the SASBoy would replace an aging EMC Symmetrix as primary storage.

"The BladeCenter and our switches in that data centre already throttle back power in the evening when I/O isn't present," Funaro said. "Adding that kind of power savings was something we considered with all our new data centres."

For the radiology clinics, business isn't always coming in at a consistent rate and none of the clinics operate 24 hours a day. "Sometimes they may have no cases, other times they might have an appointment in the morning and the next study isn't done until three hours later," Funaro said. "Why have the storage spinning all that time? If there is a busy day, the array will stay spinning automatically."

Nexsan's approach to MAID also allows users to customise tiers of spin-down within the box according to policy. Level 1 parks the drive head, and Nexsan claims this offers 20% power savings. Level 2 puts the drive into "sleep mode" for a 40% savings, and Level 3 powers the drive down completely. Users can also set volumes to cycle through those levels according to the amount of idle time. So after 10 minutes the drive might go to Level 1, after 20 minutes to Level 2 and after an hour to Level 3.

At Level 3, response time for the drives is significantly curtailed to between one minute and two minutes - within the time-out limits of Fibre Channel, but not the kind of performance users expect from 15,000 rpm SAS drives. At Level 1, according to Woolery, response time will still be less than one second.

"I know it's not going to save us a thousand dollars a day on power," Funaro said. "But if you can take 10 of your devices and add green technology, those pennies start to add up."