It seems like we’ve been waiting forever for this, but it’s finally here. Intel has added SSD TRIM capability to RAID arrays with the latest version of their RST drivers (11 and up) to 7-series motherboards. TRIM is important because without it, data that is deleted wouldn’t be freed up for use again until the drive is at a fully used state.
TRIM works with the OS to find deleted data (in Windows, this would be data that has been deleted from the recycle bin, or force-deleted, or a freshly formatted drive) and zero the flash, making it ‘good as new’. This must be supported by the SSD, firmware, OS, and drivers for everything to work. This is separate from idle garbage collection that some drives have.
Until now, this feature was not available in Intel’s storage drivers when SSDs are used in RAID mode. SSD TRIM was only offered to single drives.
To test this, we’ll take a pair of Intel 520 Series SSDs, and set them up as a RAID0 array using the latest 10.x drivers. Here’s the kind of performance you can expect from a fresh RAID0 array using a pair of fast SandForce controlled SSDs:
1085 MB/s sequential read speed? With up to 1642 MB/s burst? Yeah, that should make for a pretty snappy system.
Next we’ll put the drive into a ‘horribly used’ state by writing 128KB sequential files to it twice over, then scrambling it with random 4KB data for half an hour. After that, we simply format the drive, which should force it to TRIM the data, making it just about as good as new:
This is what your beautiful RAID array looks like without the benefit of TRIM. Eventually, the performance would continue to drop until it reaches well beyond the point of a slower single-drive SSD partition.
Now look what happens when we do the same thing with the new RST 11.2 drivers:
And there you have it, SSD RAID TRIM is working fine. The data was correctly ‘zeroed’ when the partition was formatted, instead of remaining filled with the garbage data we wrote to it.
The only issue I have with this new functionality is that it only works with 7 series chipsets. This seems to be a software-only limitation, because there is no reason why 6 series hardware shouldn’t be able to do the same. Perhaps they’ll add it in the future, or perhaps they’ll leave it this way to give people another reason to upgrade. We’ll have to wait and see.
Note that for the purposes of TRIM testing, we’re only going to be looking at sequential data transfer. This doesn’t tell the full story of SSD performance of course, but for our purposes today, it will definitely tell us whether TRIM is doing its job or not. Just keep in mind that we’re not saying anything about the overall performance of SSD RAID (although we might have to now that it is a viable option!) For more details on why it’s important to thoroughly test SSD performance using several different methods, check out one of our SSD reviews, such as our latest Kingston V200 review.
