Open Stack

On Tue, Oct 28, 2014 at 9:27 AM, Dan Genin <daniel.genin at jhuapl.edu> wrote:

>  So this brings us back to the original proposal of having separate
> backing files for Cinder and Nova which Dean thought might take too much
> space.
>

Between Cinder, Nova and Swift (and Ceph, etc) everybody wants some
loopback disk images.  DevStack's Swift and Ceph configurations assume
loopback devices and do no sharing.


> Duncan, could you please elaborate on the pain a single volume group is
> likely to cause for Cinder? Is it a show stopper?
>

Back in the day, DevStack was built to configure Cinder (and Nova Volume
before that) to use a specific existing volume group (VOLUME_GROUP_NAME) or
create a loopback file if necessary.  With the help of VOLUME_NAME_PREFIX
and volume_name_template DevStack knew which logical volumes belong to
Cinder and could Do The Right Thing.

With three loopback files being created, all wanting larger and larger
defaults, adding a fourth becomes Just One More Thing.  If Nova's use of
LVM is similar enough to Cinder's (uses deterministic naming for the LVs)
I'm betting we could make it work.

dt

-- 

Dean Troyer
dtroyer at gmail.com
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