Dot Hill 2522 review

Dot Hill has always focused on OEM deals with a wide range of blue chip clients. This year it opened up for direct sales, and it gets the ball rolling with the 2522 disk array, which it claims is the market's first 2U 24-drive SFF RAID array.

The 2522 is a DAS disk array with room for up to 24 hot-swap SFF hard disks. Note the base unit only accepts SAS drives, with the review model coming with a full complement of 73GB Seagate Savvio disks.

They don't match 3.5in hard disks for capacity, but SFF drives have a lot of benefits. Reduced power consumption makes them much greener and a lower heat output means more modest cooling requirements. Reduced vibration is another potential benefit, as the smaller drives have a lower transmitted vibration than 3.5in drives during operation.

Dot Hill offers the 2522 with either single or dual RAID controllers, where the latter function in active/active mode. Each controller has two SAS ports for host connections and is designed primarily to support two systems, where it provides primary and secondary paths to each one for failover. Expansion is an option, as the 2522 supports a total of 96 drives and the extra JBODs can either be SAS or SATA versions.

The controllers offer a couple of unique features called EcoStor and SimulCache. The former replaces traditional battery backup packs with a combination of capacitor and CompactFlash card, and in the event of a power failure the cache contents are written to the card. When power is restored the capacitor takes less time to recharge, can provide full protection quicker and also has a ten-year lifespan.

SimulCache provides a high-speed link between the two controllers. Data written to one controller is synchronously mirrored to the other and it aims to improve performance by reducing internal system traffic between them.

For installation you can use a serial port connection to the CLI, but make sure you don't lose the supplied cable as the small port on the controller is proprietary. We dispensed with this and pointed a browser at the primary controller's default IP address, and were greeted by Dot Hill's slick new RAIDar 2 web management interface.

A quick start wizard runs through configuration, and then a provisioning wizard runs through selecting member drives from the smart graphic, choosing a RAID array and choosing a preferred controller. Hot-sparing is supported and you can have up to eight dedicated and eight global hot-spares.

Note that you can't change the RAID array type later on, but volume sizes, apart from mirrors, can be expanded on the fly. Dot Hill's AssuredSnap provides snapshots that take point-in-time volume copies and store them in a snapshot pool, which is maintained in the first vdisk created. The optional AssuredCopy upgrade provides a full volume copy service.