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Dear Joe,<br>
<br>
Thanks for your kind reply, your informations are helpful. I'm
reading the imagecache.py[1] sourcecode in order to really
understand what it'll happen in case of a shared filesystem.<br>
<br>
I understand the SHA1 hash mechanism and the backing file check but
I'm not sure how it will manage the case of shared FS.<br>
<br>
The main function seems to be :<br>
- backing_file = libvirt_utils.get_disk_backing_file(disk_path)<br>
<br>
But does libvirt_utils.get_disk_backing_file federates all the
compute nodes informations ?! If no it may delete the other nodes
images ?<br>
<br>
Hope it's not too redundant,<br>
Kind regards<br>
<br>
[1]
<a class="moz-txt-link-freetext" href="https://github.com/openstack/nova/blob/master/nova/virt/libvirt/imagecache.py">https://github.com/openstack/nova/blob/master/nova/virt/libvirt/imagecache.py</a><br>
<br>
<div class="moz-cite-prefix">Le 28/04/2015 16:18, Joe Topjian a
écrit :<br>
</div>
<blockquote
cite="mid:CA+y7hvgWtXNW3vUWFw6Cq=qsLjAiRir1vW-iznmS9kHFbXwcWQ@mail.gmail.com"
type="cite">
<div dir="ltr">Hello,
<div><br>
<div class="gmail_extra">
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
I've got a similar question about cache-manager and the
presence of a shared filesystem for instances images.<br>
I'm currently reading the source code in order to find
out how this is managed but before I would be curious
how you achieve this on production servers.<br>
<br>
For example images not used by compute node A will
probably be cleaned on the shared FS despite the fact
that compute B use it, that's the main problem.<br>
</blockquote>
<div><br>
</div>
<div>This used to be a problem, but AFAIK it should not
happen any more. If you're noticing it happening, please
raise a flag.</div>
<div> </div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">How
do you handle _base guys ?<br>
</blockquote>
<div><br>
</div>
<div>We configure Nova to not have instances rely on _base
files. We found it to be too dangerous of a single point
of failure. For example, we ran into the scenario you
described a few years ago before it was fixed. Bugs are
one thing, but there are a lot of other ways a _base
file can become corrupt or removed. Even if those
scenarios are rare, the results are damaging enough for
us to totally forgo reliance of _base files.</div>
<div><br>
</div>
<div>Padraig Brady has an awesome article that details the
many ways you can configure _base and instance files:</div>
<div><br>
</div>
<div><a moz-do-not-send="true"
href="http://www.pixelbeat.org/docs/openstack_libvirt_images/">http://www.pixelbeat.org/docs/openstack_libvirt_images/</a><br>
</div>
<div><br>
</div>
<div>I'm looping -operators into this thread for input on
further ways to handle _base. You might also be able to
find some other methods by searching the -operators
mailing list archive.</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Joe</div>
<div><br>
</div>
</div>
</div>
</div>
</div>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Leslie-Alexandre DENIS
Tel +33 6 83 88 34 01
Skype ladenis-dc4
BBM PIN 7F78C3BD
SIRET 800 458 663 00013</pre>
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