Re: [Xen-users] Trim support for domU

[Radoslaw Szkodzinski <astralstorm@xxxxxxxxx>]

On Mon, Jul 9, 2012 at 7:51 AM, Liwei <xieliwei@xxxxxxxxx> wrote:
> However, can any dev clarify how trim could work on non-PV machines,
> and even on LVM? My original impression was that it'd only be remotely
> possible by passing in the whole SSD, but Casey seems to have it
> working on a LVM volume on an SSD. Thanks!

LVM supports TRIM reasonably well since I think 2.6.28. However it
will reduce the efficiency of trimming, since the Physical Volume
slice size is typically single megabytes.
I'm also not certain whether it supports TRIM in its RAID setups,
would have to check the code.

I don't know if blktap2 supports TRIM - or any Linux filesystem for
single file modifications for that matter, even if the file is sparse
- and blktap2 works via the filesystem's AIO/O_DIRECT interfaces.
However you could always try copying the image in sparse mode and
remove the original. (cp --sparse=always)

-- 
RadosÅaw SzkodziÅski

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