[Openstack-operators] rbd ephemeral storage, very slow deleting...

Scott Kohler scott_kohler at sil.org
Thu Sep 25 01:31:32 UTC 2014

True - I don't believe we have volume_clear set, and the volume sizes are
10G - 50G.


On Wed, Sep 24, 2014 at 6:25 PM, Chris Friesen <chris.friesen at windriver.com>

> On 09/24/2014 02:43 PM, Scott Kohler wrote:
>> On 09/24/2014 04:29 PM, Abel Lopez wrote:
>>> This is expected behavior, unfortunately.
>>> I spoke to the ceph guys about this last year. When you delete an
>>> ‘image’ from a pool, the monitors (IIRC) don’t instantly know where all the
>>> segments are across all the OSDs, so it takes a while to find/delete each
>>> one.
>> We also saw this, and were especially alarmed at the high CPU load on
>> deletion. So we came up with a work-around that also makes for very fast
>> instance creation as well as deletion, if you are using Ceph:
>> Create a volume from the image first, then create an instance from that
>> bootable volume. Volume creation/deletion is quite fast, with down side
>> of a two-step process. We have a CLI script that has an instance up and
>> ssh-able in less than 4 minutes, including volume creation. booting and
>> selinux recalc on first boot. Deletes take about 30 seconds. FWIW.
> Presumably the resource reclamation time is affected by the volume_clear
> setting and volume size?  I'm guessing it'd take longer than 30 seconds to
> zero out a large volume.
> Chris
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Scott Kohler
SIL GTIS SysAdmin Mgr
+1 (704) 843-6658
GTIS Systems status, see https://twitter.com/GTISNC
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