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RAIDing the SSD: Intel's 32GB SLC SSD

In pairs, and quads...
Mon Dec 22 2008, 18:07

THE OTHER DAY, we saw that these new shiny SSDs, with ten channel flash arrays aided by efficient controllers and DRAM buffers for spread out writes, do achieve some nasty benchmark results. What happens when we put two or four of them in parallel as a RAID0 stripe?

I took two of the Intel 32GB SLC high speed "enterprise class" drives and set up the RAID using the inbuilt Intel chipset controller. Ran the Vista disk bandwidth and removable device iops benchmarks. How about the results?


With two drives, each on its own SATA channel, the average read speed climbs to an astonishing 468 MB/s, actually nearing the half a gigabyte per second number almost half of the time - not bad at all and, still at the same below 1ms access time.

So, two drives in this case really do seem to double the total performance. How about, say... four? After all, we've got six SATA channels in there and, after this array plus the OS HDD and the SATA DVD, there are still two ports left.

OK, I added two more drives and recreated a fresh four-disk RAID0 array. Ran the benchmarks again...

Oh well, the read speed remained nearly the same, at 476 MB/s average, while the 74K ops/minute number did go lower than either the two or one drive configurations. Why? The south bridge SATA controller's total bandwidth could be an issue here, as well as the DMI bandwidth to the North Bridge and memory, which all could limit the net transfer rate. There's no reason why at least the read bandwidth shouldn't near double again when jumping from dual to quad parallel drive RAID0 setup.

Frankly, I'd rather stick with a two-disk RAID0 here, and consider RAID5 or RAID10 for anything more - the incremental performance benefits from two to four are non-existent on the Intel south bridge RAID controller at least, and - for safety sake - some fault tolerance would be welcome. It may be, in any case, useful to try this four-disk RAID0 configuration speed-wise on a true hardware RAID controller, which I'm about to do as well. µ


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