Le 07/03/2016 17:58, Jason Dillaman a écrit :
> Documentation of these new RBD features is definitely lacking and
I've opened a tracker ticket to improve it [1].
>
> [1] http://tracker.ceph.com/issues/15000
>
Hey, thank you Jason! :)
> That's disheartening to hear that your RBD images were corrupted --
do you have any more detail as to what happened? Enabling the object
map is designed to flag the object map as invalid, so it won't be used
as a reference for any IO ops until it is successfully rebuilt.
>
No problem at all, as it was just a test. As I saw the VM losing its
disk (the file system wasn't available anymore even for a remount), the
VM went all "IO error" on every disk access, but the shell was still there.
Infernalis 9.2.0 (it was the day just before the 9.2.1 bugfix release :)
). KVM + QEMU + libvirt with RBD disks on the QEMU side.
The RBDs only had the layering feature enabled.
With the VMs powered on, I enabled the exclusive-lock, the object map
and fast-diff features. I then proceeded rebuilding the object-map in
order to test the "rbd du" command... and get rid of some pesky
invalid-object-map-related warnings. Yes, some warning showed up when I
typed "rbd info XXX" or "rbd du XX" before successfully compiling the
object-map.
The object-map rebuild process started with more of these "warnings",
ran for a while showing the completion percentage as it's supposed to,
but it presented me some more warnings at the end. Meanwhile, in
VM-land, the disk was inaccessible from the kernel point of view, ext4
presented me its best "goodbye cruel world" testament, while, naturally,
the shell reacted with a nice IO error at every attempt of running
external programs. Clearly, with any IO interrupted until next reboot,
for us any on-disk data is considered as corrupted.
Did the "rbd rebuild" process take the exclusive-lock on the RBD ?
I'm re-testing this while I'm typing, on infernalis 9.2.1.
Added the exclusive-lock, object-map and fast-diff features, a lot of
sweating on my side, but the guest kernel didn't blink.
Started rebuilding the object-map aaaaand...
Object Map Rebuild: 99% complete...failed.
rbd: rebuilding object map failed: (16) Device or resource busy
The VM continues working without interruption.
Non-intensive but continuous IO on the guest filesystem was ongoing the
whole time.
Stopped any IO, launched the rebuild, same "busy" message.
Stopped the VM, rebuild.
Object Map Rebuild: 100% complete...done.
That's a lot better than the previous experience. :)
Thanks
Loris
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