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Hello,

I thought I would post this due to the frequent Gluster talk on the list:

Just an FYI for anyone thinking of using this volume driver: make sure you
are using a kernel greater than 3.3. For Ubuntu 12.04, the 3.4 kernel found
here works:
http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.4-precise/

The reason for this is that Nova tries to attach the volume using
cache="none". This requires the filesystem to support O_DIRECT, which is
only available for FUSE-based filesystems in kernels above 3.3.

When trying to attach a gluster-based volume to an instance on a compute
node that runs a kernel below 3.3 (eg the stock Ubuntu 12.04 kernel), you
will get a very helpful error message of "DeviceIsBusy: The supplied device
(vdx) is busy)"...

Hopefully this saves someone the 2 hours of troubleshooting that I went
through to figure out the real answer  :)

This morning I went to file a bug and saw one has already filed:
https://bugs.launchpad.net/nova/+bug/1177103

I love when that happens when you already know the answer you're looking
for  :)

I will also be amending the Gluster volume driver docs to note this.

Finally, this issue seems to be resolved for using Gluster as an instance
store. If I remember right, I ran into this same issue several months ago
and it was resolved by updating the kernel. Seems like Grizzly correctly
detects if O_DIRECT is available or not.

Thanks,
Joe

-- 
Joe Topjian
Systems Administrator
Cybera Inc.

www.cybera.ca

Cybera is a not-for-profit organization that works to spur and support
innovation, for the economic benefit of Alberta, through the use
of cyberinfrastructure.
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