>
Apparently drives with the Sandforce SF 1200 or SF1500 controller have built-in "garbage collection" and "wear leveling" that does the same thing as Trim.
Almost all SSDs have wear levelling and garbage collection - if they didn't then commonly-used sectors of the drive would wear out very quickly and the drive would die a premature death.
This is not the same as TRIM.
TRIM is a new command that's been added to the SATA and SAS command sets. It's issued by the OS to let the drive know when sectors have been freed up. So the OS has to be smart enough to issue TRIM commands, and the drive has to be smart enough to accept and process them.
To do garbage collection and wear leveling an SSD needs to have unused sectors. The problem is that if the OS writes data to a sector then the drive has to assume the sector contains useful data and it can no longer be treated as being free for wear leveling. And over time the OS will write to most of the sectors on the drive, so the SSD won't have very many free sectors it can use.
What TRIM is for is to let the OS tell the drive when it no longer needs sectors - the SSD can then use those sectors for wear leveling. When the OS deletes a file
it normally doesn't do anything more than remove it's directory entry and update it's freespace map. The actual data in the file isn't touched - that's why there are utilities that can recover deleted files. Because of this,
the SSD is not aware that those sectors are no longer needed.
But if the OS knows it's talking to an SSD then it issues TRIM commands for the data sectors in each file that it deletes so that the SSD can put use those sectors for wear leveling.
>
This drive from OWC claims to accept Trim commands while in Raid, please read as it is contradicting you.
>
http://eshop.macsales.com/item/Other%20World%20Computing/SSDMXRE050/
There's nothing on the page you linked that makes that claim. The page merely says the drive is "RAID ready" and that it "supports TRIM". But that has nothing to do with whether the TRIM commands will make it from the OS to the drive.
It's not the DRIVE that needs some special feature to use TRIM in a RAID array, it's the RAID CONTROLLER. The RAID controller has to report to Windows that the speed of the logical RAID volume is "0 RPM" in order for Windows to recognize it as using SSD storage. When Windows so recognizes a drive it will issue the necessary TRIM commands to it.
And the RAID controller must accept the those TRIM commands remap it to the appropriate sectors on the member drives and re-issue it to the disks.
I've not yet seen confirmation that any RAID controller can do this. The ICHxxR drivers for Intel chipset RAID will pass TRIM commands to an SSD, but only if the SSD is NOT configured as part of a RAID array. See:
http://techreport.com/discussions.x/18653