On Mon, Mar 8, 2021 at 8:15 AM Alex McWhirter <[email protected]> wrote:

> I apologize for the spam, this seems to be a long standing gluster issue.
> https://github.com/gluster/glusterfs/issues/597
>
> sharding does not support SEEK_DATA/SEEK_HOLE, with a preallocated image
> you likely never see this issue as there are no holes. However with a
> sparse image, that's very much not the case. I'm not sure when qemu-img
> changed to use these syscalls, as this is not something i experience on 4.3
> / CentOS 7.
>
> I'd be interested if anyone else can replicate this image copy behavior
> using raw sparse (thin provision) disks as the source on a gluster volume
> with sharding enabled, on oVirt 4.4.4+ (possibly earlier is also affected)
>
> If this is something current qemu-img cannot handle, i don't think
> supporting sparse disks on sharded gluster volumes is wise.
>
>
>
I only remember for sure that with 4.4.0 (and perhaps up to 4.4.2) with
single host HCI with Gluster I couldn't use sharding in a lab where I had
to create, destroy and recreate many times an Openshift environment
composed by many VMs and having thin disks was a must to improve times.
I sent several messages regarding this to the list but no active resolution
and was forced to disable sharding.

I also wrote to Gluster guys.

I can try to search and send the links.

Gianluca
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