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Old 05-23-2011, 07:57 AM   #1
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RAID 1 SSD drives with TRIM

I'm looking to setup a system with mirrored SSD drives, i'd like to have TRIM support, and I am finding conflicting information. Some articles say TRIM doesn't work with drives in RAID, some say it will work with a RAID controller but not with drives configured in a RAID set, and others say that it works with RAID but not RAID5 and doesn't go into detail beyond that.

So can I get a mirrored set of SSD's with TRIM support? What chipset? Does anyone have any experience with this? Thanks if you can help!
Old 06-01-2011, 08:12 AM   #2
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The RHEL Storage Administration Guide has this warning about using RAID with SSDs:
In addition, keep in mind that MD (software raid) does not support discards. In contrast, the logical volume manager (LVM) and the device-mapper (DM) targets that LVM uses do support discards. The only DM targets that do not support discards are dm-snapshot, dm-crypt, and dm-raid45. Discard support for the dm-mirror was added in Red Hat Enterprise Linux 6.1.

Red Hat also warns that software RAID levels 1, 4, 5, and 6 are not recommended for use on SSDs. During the initialization stage of these RAID levels, some RAID management utilities (such as mdadm) write to all of the blocks on the storage device to ensure that checksums operate properly. This will cause the performance of the SSD to degrade quickly.
Old 06-05-2011, 08:44 AM   #3
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I have yet to see TRIM working automatically in any filesystem. If you wanted to use TRIM manually (with & hdparm, which only works on the ocz vertex series) you can, however not with a raid since the script needs a block device not a raid device. So to answer your question, I don't know of any scripts/raid cards/software that can actually use TRIM. I do know that it is possible on some SSD's that aren't raided together.


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