Intel to Add TRIM Support for RAID 0
by Kristian Vättö on November 21, 2011 2:35 AM ESTIntel's release notes for Rapid Storage Technology (RST) 11.5 Alpha version reveal that they have plans to add TRIM support for RAID 0 arrays in the next version of RST. Windows 7 and Intel's RST have supported TRIM for quite a while, but the support has always excluded RAID 0 arrays. We don't know when the RST version with TRIM will arrive but given that the Alpha version dates back to August 5th, a newer version with TRIM should be expected sooner than later.
The benefits of TRIM are obvious because the write performance of an SSD will degrade in the long run without TRIM (or good garbage collection). Here is a quick brief on what TRIM is and what it does. TRIM is a simple command that allows the OS to inform the SSD controller what files are no longer in use (i.e. have been deleted). NAND flash doesn't allow individual pages to be erased; only a block can be erased. This causes problems because without TRIM, the OS just marks the deleted files as empty space, meaning that the actual data is not erased from the drive. When you run out of free blocks, you first have to read the whole block to cache before you can erase and then re-write the block. That means instead of a simple write, the SSD has to do a read, and erase, and then a write, which is why the write speed in degraded mode is much slower. For more detailed explanation on TRIM, take a look at our The SSD Anthology article.
For users who run SSDs in RAID 0, this is great news. While RAID 0 always introduces reliability concerns, the lack of TRIM is another obstacle for many. High capacity SSDs still cost a hefty premium, and putting two smaller SSDs in RAID 0 can save you a few bucks, plus you get increased read and write speeds.
Source: Intel via StorageReview
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Mugur - Monday, November 21, 2011 - link
Maybe I'm just ignorant, but I don't remember reading that there is TRIM support for RAID 1 either... :-)Phylyp - Monday, November 21, 2011 - link
Agreed - I was always under the impression that having a RAID setup meant forgoing TRIM support. Kristian, could you clarify, please?Kristian Vättö - Monday, November 21, 2011 - link
As far as I know, TRIM does not work with RAID 1 arrays either. RAID is kind of a layer between the physical drives and the OS, so it needs a bit extra work to be supported by TRIM. I guess RAID 1 support will follow later on but RAID 0 is more popular (at least among consumers) so supporting it first makes sense.RMSe17 - Monday, November 21, 2011 - link
Right, the RAID controller did not propagate the TRIM commands, since they were not built into the controller, at least that's how Intel SSD guys explained it. My guess is that if RAID 0 is supported, RAID 1 will be supported as well, because the RAID controller will propagate TRIM.Kristian Vättö - Monday, November 21, 2011 - link
Intel's release notes mention only RAID 0 (it's the Intel link at the end of the article).bunnyfubbles - Monday, November 21, 2011 - link
I think the stipulation might be there because TRIM will work when you have RAID mode enabled for the Intel SATA controller as long as the drive isn't in an actual RAID "array"Basically IRST will successfully employ TRIM to any single SSD as long as the controller is configured as AHCI or RAID, which is a fairly common voiced concern from newer SSD users as they hear they need AHCI for TRIM to work but do not know that Intel's RAID mode will also work (again, as long as the SSD isn't actually in an array)
kyuu - Monday, November 21, 2011 - link
Great news. I was looking at adding a second identical SSD to my system for added capacity and in RAID 0 for performance benefits, but the lack of TRIM support was making me wonder if it'd be worth it.probedb - Monday, November 21, 2011 - link
I've still not found a version of RST that doesn't stop this from working on their own chipset. With this installed I can't safely eject SATA drives even when set to Hot Swap in the BIOS. Uninstall and it works fine.QQuxa - Monday, November 21, 2011 - link
how would raid-0 help with capacity premium? two smaller drives in raid-0 will do nothing for capacity..Slash3 - Monday, November 21, 2011 - link
Actually, no. Two identical drives in RAID 0 (striping) will result in a single volume with the capacity of both. Two 120GB SSDs in RAID 0 nets you a single 240GB storage device for your OS to see.RAID 1, on the other hand, is mirroring. This effectvely halves the capacity of the drives in the set, because half is used to create a redundant copy.