[PVE-User] BTRFS...

Gilberto Nunes gilberto.nunes32 at gmail.com
Tue Feb 2 17:58:35 CET 2016


Well

I think the opposite what you suggest... I want use btrfs inside the KVM
guest, in order to increase/decrease the size oh disk partition...


2016-02-02 14:53 GMT-02:00 brian mullan <bmullan.mail at gmail.com>:

> Gilberto,
>
> I have used btrfs for almost 2 years and like it alot for its features.
> I've not used it with proxmox though.
>
> Matter of fact I just changed my machine to use btrfs raid10 (btrfs raid
> not mdm raid).   In btrfs this is only 1 command:
>
> reference:  btrfs with multiple devices <https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices>
> example:
> # Use raid10 for both data and metadata
> mkfs.btrfs -m raid10 -d raid10 /dev/sdb /dev/sdc /dev/sdd /dev/sde
>
>
> However, I have learned a lot over that time also.
>
> First, I don't think its yet recommended to run KVM on btrfs.  This could
> have changed but it would be wise to understand what the concerns were.
>
> I think it had to do with the COW algorithm of btrfs will churn with every
> change made to the running kvm 'image" file... causing high cpu etc.
>
> reference:    http://www.linux-kvm.org/page/Tuning_KVM
>
> see the statement at the bottom...
> *Don't use the linux filesystem btrfs on the host for the image files. It
> will result in low IO performance. The kvm guest may even freeze when high
> IO traffic is done on the guest. *
>
> However, LXC containers on the other hand actually work wonderfully with
> btrfs as you can specify the LXC container "backingstore" to be btrfs and
> cloning, etc becomes almost instantaneous.
>
>
>
>
> *If 'btrfs' is specified, then the target filesystem must be btrfs,  and the  container rootfs will be created as a new subvolume. This allows snapshotted clones to be created, but also causes rsync --one-filesystem to treat it as a separate  filesystem.*
>
>
> So today I have my KVM images run off an ext4 disk but my lxc containers
> are on my main btrfs raid10.
>
> Others may have better insight.
>
> Brian
>
>


-- 

Gilberto Ferreira
+55 (47) 9676-7530
Skype: gilberto.nunes36
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