LXC LVM-thin discard fstrim

[TECOB]

Hi,

We are running a server with several LXC containers. This server data pool is under LVM-thin and as time goes by, disk space keeps on increasing. Even if files are deleted on LXC containers, data % on host stays the same.

We have seen that running fstrim on LXC containers freed space on Host and so, data percentage was reduced.

In /etc/lvm/lvm.conf issue_discards is enabled (1)
Running
$ lvs -o+discards pve/data
shows discards option as 'passdown'

Have we missed a configuration? Isn't it supposed to reduce space automatically when files are deteled on LXC containers?
Should we run fstrim service on LXC containers periodically to free space?

Have someone met this situation? How could we solve that?

Regards,

Jordi.

 

[kobuki]

The LCX root volumes are mounted without the ext4 discard flag, so I guess it's not automated. It would be really useful to be able to set the mount options or at least discard.

I've put together this small scritp for my test server to aid in a weekly fstrim task. Maybe it helps someone...

#!/bin/bash

# static list of volumes to trim
TRIMVOLS="/"

FSTRIM=/sbin/fstrim

# trim static list
for i in $TRIMVOLS; do
  $FSTRIM -v $i 2>&1 | logger -t "fstrim-cron[$$]"
done

# trim all LXC containers
for i in $(pct list | awk '/^[0-9]/ {print $1}'); do
  $FSTRIM -v /proc/$(lxc-info -n $i -p | awk '{print $2}')/root 2>&1
done | logger -t "fstrim-cron[$$]"