Promise SmartStor DS4600 review

The SmartStor DS4600 is a direct attached storage (DAS) appliance with four 3.5in hot-swappable drive bays. It’s basically the same as the SmartStor NS4600, but with no network support: rather, it connects directly to your PC via USB 2 or eSATA, and for Mac users, FireWire 400 and 800 are also offered.

The unit’s abilities depend on how many drives you install. Fit one drive and it will work just like an expensive external hard disk enclosure. Move up to two drives and RAID 0 striping and RAID 1 mirroring become available. With three drives, RAID 5 becomes an option, offering a balance between fault-tolerance and storage capacity. And if you fully populate the SmartStor with four drives you can enjoy RAID 10 – two disks combined into a RAID 0 array and mirrored onto the other two disks. If you can’t decide which sort of array to use, press the one-click setup button and the DS4600 will automatically select and build one for you, based on the number of disks installed.

We tested the SmartStor’s performance using four Western Digital RE4 2TB enterprise drives. Over a USB 2 connection, the RAID mode we used had little effect on performance: in four-disk RAID 0, RAID 5 and RAID 10 configurations, we saw average read and write speeds of 30MB/sec and 53MB/sec respectively. That’s a typical read rate, but unusually fast write performance. We’ve seen few external drives that can handle more than around 30MB/sec over USB 2.

Our small file tests went similarly. The average read rate was an unremarkable 22MB/sec, but in RAID 0 and RAID 10 mode write performance was again unusually strong, at 41MB/sec. The system only slowed down in RAID 5 mode, writing our files at an average rate of 30MB/sec, thanks no doubt to the overhead of calculating and distributing parity information.

Switching to the much faster eSATA connection permitted the SmartStor to reveal its full performance potential. In RAID 0 mode, large file read and write speeds were 114MB/sec and 186MB/sec respectively, with small files coming in at 59MB/sec and 115MB/sec. Moving to RAID 5 improved performance in our large file tests, raising speeds to 173MB/sec and 208MB/sec, but small files were more mixed, with read speeds rising to 71MB/sec while write speeds dropped to 85MB/sec.

The SmartStor DS4600’s best performance was in RAID 10 mode over eSATA, where it read and wrote large files at average rates of 170MB/sec and 227MB/sec, with small files coming in at 74MB/sec and 122MB/sec. These are very respectable scores, but they don’t show much benefit from striping: we’d expect to see similar scores from a single-drive eSATA enclosure using a fast modern disk such as the Samsung Spinpoint F3.