[openstack-dev] [nova][cinder] Extending attached disks

[Taylor . Bertie]

Hi everyone,

In my current pre-production deployment we were looking for a method to live extend attached volumes to an instance. This was one of the requirements for deployment. I've worked with libvirt hypervisors before so it didn't take long to find a workable solution. However I'm not sure how transferable this will be across deployment models. Our deployment model is using libvirt for nova and ceph for backend storage. This means obviously libvirt is using rdb to connect to volumes.

Currently the method I use is:

- Force cinder to run an extend operation.

- Tell Libvirt that the attached disk has been extended.

It would be worth discussing if this can be ported to upstream such that the API can handle the leg work, rather than this current manual method.

Detailed instructions.

You will need: volume-id of volume you want to resize, hypervisor_hostname and instance_name from instance volume is attached to.

Example: extending volume f9fa66ab-b29a-40f6-b4f4-e9c64a155738 attached to instance-00000012 on node-6 to 100GB

$ cinder reset-state --state available f9fa66ab-b29a-40f6-b4f4-e9c64a155738

$ cinder extend f9fa66ab-b29a-40f6-b4f4-e9c64a155738 100

$ cinder reset-state --state in-use f9fa66ab-b29a-40f6-b4f4-e9c64a155738

$ssh node-6

node-6$ virsh qemu-monitor-command instance-00000012 --hmp "info block" | grep f9fa66ab-b29a-40f6-b4f4-e9c64a155738

drive-virtio-disk1: removable=0 io-status=ok file=rbd:volumes-slow/volume-f9fa66ab-b29a-40f6-b4f4-e9c64a155738:id=cinder:key=<keyhere>==:auth_supported=cephx\\;none:mon_host=10.1.226.64\\:6789\\;10.1.226.65\\:6789\\;10.1.226.66\\:6789 ro=0 drv=raw encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0

This will get you the disk-id, which in this case is drive-virtio-disk1.

node-6$ virsh qemu-monitor-command instance-00000012 --hmp "block_resize drive-virtio-disk1 100G"

Finally, you need to perform a drive rescan on the actual instance and resize and extend the file-system. This will be OS specific.

I've tested this a few times and it seems very reliable.

Taylor Bertie
Enterprise Support Infrastructure Engineer

Mobile +64 27 952 3949
Phone +64 4 462 5030
Email taylor.ber...@solnet.co.nz

Solnet Solutions Limited
Level 12, Solnet House
70 The Terrace, Wellington 6011
PO Box 397, Wellington 6140

www.solnet.co.nz 

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