How to create a striped LVM thin-pool?

LXD Support
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1

It is in principle possible to create a striped thin pool with native lvm tools. That info I can find.

Yet with ‘lxc storage …’ I fail to do so. On ‘linuxcontainers’ I’ve read it should be possible, yet when passing ‘lvm.stripes=X’ I’m always told that it is not possible for thin pools or thin volumes.

Background:

I’m having IO limiting issues on a server. The thin pool lives in a volume group with 3 SSDs, so I’d like to have 3 stripes to hopefully speed up things. Possible data loss on drive failure doesn’t concern me at the moment. Sequential IO is decent (for one stripe), yet random IO is … rather sad.

2

Can you show your reproducer steps please?

Also please show the precise error you get.

Thanks

3

LXD_LVM: existing volume group with some free space

Using the reference: https://documentation.ubuntu.com/lxd/en/latest/reference/storage_lvm/

lvm.stripes string same as volume.lvm.stripes Number of stripes to use for new volumes (or thin pool volume)

root@debian:~# lxc storage volume create LXD_LVM test-vol lvm.stripes=3
Error: lvm.stripes cannot be used with thin pool volumes

This made me search a bit further and I found that with lvm tools itself I would have to create a striped thin pool myself.

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/logical_volume_manager_administration/thinly_provisioned_volume_creation

Unfortunately LXD is not really good at just using that. I’d have to mess with internal configs.

I could use a stacked LVM setup, but that just doesn’t feel right, e.g. create a striped logical volume manually and use that to “feed” lxd and have it create its thin-pool using that.

I may be misreading the reference, but to me it looks like lxd should support striped thin pool volumes out of the box.

4

And the volume group is backed by multiple disks?

Can you show lvs output please.

5

I’ve gained a few more insights.

  1. ‘lvs’ does not show stripes of anything with the default view, it has to be ‘lvs -o+stripes’
  2. ‘-a’ must be added as well, to show thin pool ‘tmeta’ and ‘tdata’. The latter is striped if created accordingly.

For posterity:

These two articles were very helpful. They deal with creating / using a striped (thin) pool

  1. https://discuss.linuxcontainers.org/t/weekly-status-131/6545
  2. https://askubuntu.com/questions/1222407/setup-lxd-storage-thin-pool-on-an-existing-lvm-volume-group-of-the-host

This would be a good topic for a ‘howto’

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