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To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: TRIM on XFS
From: Jeffrey Hundstad <jeffrey.hundstad@xxxxxxxx>
Date: Tue, 11 Oct 2011 11:06:24 -0500
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20111011020552.GY3159@dastard>
References: <201110071352.20135@xxxxxx> <20111007233450.GK3159@dastard> <201110100829.45823@xxxxxx> <CAGpXXZJs8kjZaSp248rA+-d=gpwWe=oK0xtUUirv+zgE3Vq3kA@xxxxxxxxxxxxxx> <4E936BFB.5060907@xxxxxxxx> <20111011020552.GY3159@dastard>
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20111005 Icedove/3.1.15

Thank you. I suspected this may be the case. It is awfully nice to have a definitive answer though. It is especially nice to have a way to determine if it is possible. Thank you!

I've created a an XFS Wiki page for this info:

Jeffrey Hundstad

On 10/10/2011 09:05 PM, Dave Chinner wrote:
On Mon, Oct 10, 2011 at 05:04:43PM -0500, Jeffrey Hundstad wrote:
On 10/10/2011 03:28 PM, Greg Freemyer wrote:
fitrim is the batch mode.

To enable realtime discard, add --discard to your mount options.

Documented athttp://lxr.linux.no/#linux+v3.0.4/Documentation/filesystems/xfs.txt

To invoke batch mode, simply use fstrim from user space.

I'm also trying to use FITRIM on a simple XFS partition on a
spinning magnetic hard drive (remember those).  I haven't had much
luck.  I'm doing this just to get used to the commands when using
this against a thinly provisioned disk.  I have no idea if this
should work in this configuration.

On a Debian system with Linux 3.0.0-2-amd64 when I issue:
# fstrim /

I receive:
fstrim: /: FITRIM ioctl failed: Operation not supported

With an strace this looks like:
open("/", O_RDONLY)                     = 3
ioctl(3, 0xc0185879, 0x7fff4ea851b0)    = -1 EOPNOTSUPP (Operation
not supported)
It means the block device underneath the filesystem doesn't support
the TRIM operation. Check /sys/block/<dev>/queue/discard_max_bytes -
if the value is zero then your device doesn't support discard



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