[Users] ploop and trim/ discard support

[Kir Kolyshkin]

On Sep 12, 2012 11:20 PM, "Corin Langosch" <info at corinlangosch.com> wrote:
>
> Hi,
>
> it seems that when creating & deleting files inside a ploop backed
container the backing image file doesn't shrink. So the image file is still
consuming around 400 GB, while in the container df shows only 100 GB in use.
>
> ll on host: -rw------- 1 root root 384G Sep 12 21:06 root.hdd
> df on container: /dev/ploop1           493G  103G  390G  21% /

We have online shrink. It's "ploop balloon discard" or just "vzctl
compact". You'd better have ploop and vzctl from git (both are really close
to be released).

>
> I assume this is because ploop doesn't get informed by the ext4 fs when
blocks are no longer in use. Should it help to to mount the ext4 on the
ploop device with the "discard" option? I didn't test if it helps yet, but
at least I was able to pass the mount option (thanks to kir's recent
enhancements) and it started the container without any problems.
>
> /dev/ploop1 on / type ext4 (rw,relatime,barrier=0,data=ordered,discard)
>
> To free all "free" existing blocks I also tried to do a batch cleanup/
trim from inside the container using "fstrim /" but it doesn't work:
>
> root at test:~# fstrim /
> fstrim: /: FITRIM ioctl failed: Operation not permitted
>
> Should this be working or is it not supported yet? Am I on the right path
at all? Any better solutions? :)
>
> Corin
>
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