[kwlug-disc] SSDs and TRIM
John Van Ostrand
john at netdirect.ca
Thu Apr 29 12:49:06 EDT 2010
----- "Chris Irwin" <chris at chrisirwin.ca> wrote:
> I just ordered my birthday present: A Solid-State Disk. I made sure I
> got one with TRIM support to try and prevent the performance
> degredation seen with earlier SSDs. Now, TRIM isn't part of ext4
> Linux 2.6.34, so I can't actually have live TRIM support at the
> filesystem layer, but it appears there is a manual utility that can
> used with offline ext2/3/4 filesystems, and apparently online ext4 as
> well. (This is apparently part of hdparm now).
> BUT, has anybody been using TRIM on their LVM-backed filesystems?
> seen "No, can't be done", "Maybe it should work", and "yes, per the
> instructions in the forum". Of course the dozens of related forum
> threads have dozens of pages to sift through. I've put in a few hours
> of reading, but still have no idea what is going on. From what I
> understand, ext4's TRIM support won't work with LVM since the DM
> doesn't currently do the mapping. In theory, the third party TRIM
> utilities floating around could do it since they build their own maps
> and sector lists. Anybdoy else looked into this?
> The problem with LVM being that the filesystem isn't a flat map to a
> physical partition, and apparently nobody has done the work to build
> map to redirect TRIM commands.
Correct me if I'm ignorant, but won't putting an LVM on a dm device do what you want? You can use dm for TRIM and have the benefits of LVM.
John Van Ostrand
Net Direct Inc.
564 Weber St. N. Unit 12, Waterloo, ON N2L 5C6
Ph: 866-883-1172 x5102
Linux Solutions / IBM Hardware
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