[Gluster-users] KVM guest I/O errors with xfs backed gluster volumes

[Bharata B Rao]

On Tue, Oct 29, 2013 at 1:21 PM, Anand Avati <avati at gluster.org> wrote:

> Looks like what is happening is that qemu performs ioctls() on the backend
> to query logical_block_size (for direct IO alignment). That works on XFS,
> but fails on FUSE (hence qemu ends up performing IO with default 512
> alignment rather than 4k).
>
> Looks like this might be something we can enhance gluster driver in qemu.
> Note that glusterfs does not have an ioctl() FOP, but we could probably
> wire up a virtual xattr call for this purpose.
>
> Copying Bharata to check if he has other solutions in mind.
>

I see alignment issues and subsequent QEMU failure (pread() failing with
EINVAL) when I use a file from XFS mount point (with sectsz=4k) as a virtio
disk with cache=none QEMU option. However this failure isn't seen when I
have sectsz=512. And all this is w/o gluster. So there seems to be some
alignment issues even w/o gluster, I will debug more and get back.

Jacob - In the first mail you sent on this subject, you mention that you
don't see any issues when gluster volume is backed by ext4. Does this still
hold true ?

Regards,
Bharata.
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