Dot Hill 2522 review

The 2522 supports Microsoft's MPIO (multi-path I/O), which uses multiple hardware components to create redundant paths from hosts to storage volumes, and Dot Hill provides its DSM (device specific module) as standard. Unlike iSCSI, there's nothing to do for configuration here. If you have one physical connection to the array then one drive appears, and when you attached the second cable an MPIO link is automatically created.

For testing we called up a Broadberry CyberServe dual 2.8GHz X5560 Xeon server equipped with 12GB of DDR3 memory, and a LSI SAS3801E HBA running Windows Server 2003 R2. On the 2522 we created a five drive RAID5 array plus a dual drive stripe. With an MPIO link in action, the Iometer utility reported very impressive raw read and write throughputs on the RAID5 array of 540MB/sec and 290MB/sec. There wasn't much to see between RAID5 and the striped array with the latter returning 541MB/sec and 281MB/sec read and write speeds.

We also tested MPIO on the RAID5 array by removing one of the SAS cables while Iometer was running. The Windows Device Manager noted that one of the MPIO drives had been removed, but Iometer continued unabated, reporting a raw read throughput of 280MB/sec. With the secondary link restored performance climbed back up to 540MB/sec with no interruptions.

Along with good overall performance, the 2522 delivers in the power stakes with our inline meter measuring a draw of 312W with all drives idle. With Iometer running across all 24 drives we saw this increase only slightly to 325W.

Compared with FC and IP SAN disk arrays, the 2522 is a little pricey but it's very easy to deploy and delivers superior performance. It offers plenty of redundancy and expansion potential, while the smaller SFF hard disks have a positive impact on power consumption and cooling requirements.

Author: Dave Mitchell