On 11/20/2013 06:53 AM, nicolasc wrote:
Thank you Bernhard and Wogri. My old kernel version also explains the
format issue. Once again, sorry to have mixed that in the problem.
Back to my original inquiries, I hope someone can help me understand why:
* it is possible to create an RBD image larger than the total capacity
of the cluster
There's simply no checking of the size of the cluster by librbd.
rbd does not know whether you're about to add a bunch of capacity to the
cluster, or whether you want your storage overcommitted (and by how much).
Higher level tools like openstack cinder can provide that kind of logic,
but 'rbd create' is more of a low level tool at this time.
* a large empty image takes longer to shrink/delete than a small one
rbd doesn't keep an index of which objects exist (since doing so would
hurt write performance). The downside is as you saw, when shrinking or
deleting an image it must look for all objects above the shrink size
(deleting is like shrinking to 0 of course).
In dumpling or later rbd can do this in parallel controlled by
--rbd-concurrent-management-ops, which defaults to 10.
If you've never written to the image, you can just delete the rbd_header
and rbd_id objects for it (or just the $imagename.rbd object for format 1
images), then 'rbd rm' will be fast since it'll just remove its entry from
the rbd_directory object.
Josh
Best regards,
Nicolas Canceill
Scalable Storage Systems
SURFsara (Amsterdam, NL)
On 11/20/2013 01:56 PM, Bernhard Glomm wrote:
That might be,
manpage of
ceph version 0.72.1
tells me it isn't though.
anyhow still running kernel 3.8.xx
Bernhard
Am 19.11.2013 20:10:04, schrieb Wolfgang Hennerbichler:
On Nov 19, 2013, at 3:47 PM, Bernhard Glomm
<bernhard.glomm@xxxxxxxxxxx> wrote:
Hi Nicolas
just fyi
rbd format 2 is not supported yet by the linux kernel (module)
I believe this is wrong. I think linux supports rbd format 2
images since 3.10.
wogri
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