[Lustre-discuss] Swap on Lustre (was: Client is not accesible when OSS/OST server is down)

[Robin Humble]

On Fri, May 02, 2008 at 11:25:03AM -0700, Andreas Dilger wrote:
>On Apr 29, 2008  09:05 -0700, Kilian CAVALOTTI wrote:
>> /scratch # swapon -a ./swapfile
>> swapon: ./swapfile: Invalid argument
>
>Note that in 1.6.4+ there is an interface to export a block device
>more directly from Lustre instead of using the loopback driver on top
>of the client filesystem.  This is the "llite_loop" module and is
>configured like:
>
>	lctl blockdev_attach {loopback_filename} {blockdev_filename}
>
>where {loopback_filename} is the file that should be turned into a
>block device (it can be sparse if desired) and {blockdev_filename}
>is the full filename that the new block device should be created at.

cool! I was wondering that that module was for.
I'm trying to use it like:
  lctl blockdev_attach /dev/lloop0 /some/file/on/lustre
but then dd to /dev/lloop0 seems to go at ~kB/s wheras dd to the file
goes at >= 100MB/s. am I doing something wrong?

cheers,
robin

>To clean up the device use:
>
>	lctl blockdev_detach {blockdev_filename}
>
>Note that using this block device for swap hasn't been very successful
>in our testing so far, but we also haven't done a great deal of real
>world testing only "allocate a ton of RAM and dirty it all as fast
>as possible", which isn't a very realistic usage.  Feedback would
>be welcome.
>
>Cheers, Andreas
>--
>Andreas Dilger
>Sr. Staff Engineer, Lustre Group
>Sun Microsystems of Canada, Inc.
>
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