<div dir="ltr">Hi,<div>><span style="font-size:12.7272720336914px">Some </span><span style="font-size:12.7272720336914px">people apparently use the ‘host’ option in cinder.conf to make the hosts indistinguishable, but this creates problems in other places.</span></div><div><span style="font-size:12.7272720336914px">I use shared storage mounted on several cinder-volume nodes, with "host" flag set the same everywhere. Never ran into problems so far. Could you elaborate on "</span><span style="font-size:12.7272720336914px">this creates problems in other places" please ?</span></div><div><span style="font-size:12.7272720336914px"><br></span></div><div><span style="font-size:12.7272720336914px">Thanks !</span></div><div><span style="font-size:12.7272720336914px">Jordan</span></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Jan 8, 2015 at 3:40 PM, Arne Wiebalck <span dir="ltr"><<a href="mailto:Arne.Wiebalck@cern.ch" target="_blank">Arne.Wiebalck@cern.ch</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div>Hmm. Not sure how widespread installations with multiple Ceph backends are where the</div>
<div>Cinder hosts have access to only one of the backends (which is what you assume, right?)</div>
<div>But, yes, if the volume type names are also the same (is that also needed for this to be a</div>
<div>problem?), this will be an issue ...</div>
<div><br>
</div>
<div>So, how about providing the information the scheduler does not have by introducing an</div>
<div>additional tag to identify ‘equivalent’ backends, similar to the way some people already</div>
<div>use the ‘host’ option?</div>
<div><br>
</div>
<div>Thanks!</div><span class="HOEnZb"><font color="#888888">
<div> Arne</div></font></span><div><div class="h5">
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<blockquote type="cite">
<div>On 08 Jan 2015, at 15:11, Duncan Thomas <<a href="mailto:duncan.thomas@gmail.com" target="_blank">duncan.thomas@gmail.com</a>> wrote:</div>
<br>
<div>
<div dir="ltr">The problem is that the scheduler doesn't currently have enough info to know which backends are 'equivalent' and which aren't. e.g. If you have 2 ceph clusters as cinder backends, they are indistinguishable from each other.<br>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On 8 January 2015 at 12:14, Arne Wiebalck <span dir="ltr">
<<a href="mailto:Arne.Wiebalck@cern.ch" target="_blank">Arne.Wiebalck@cern.ch</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi,<br>
<br>
The fact that volume requests (in particular deletions) are coupled with certain Cinder hosts is not ideal from an operational perspective:<br>
if the node has meanwhile disappeared, e.g. retired, the deletion gets stuck and can only be unblocked by changing the database. Some<br>
people apparently use the ‘host’ option in cinder.conf to make the hosts indistinguishable, but this creates problems in other places.<br>
<br>
>From what I see, even for backends that would support it (such as Ceph), Cinder currently does not provide means to ensure that any of<br>
the hosts capable of performing a volume operation would be assigned the request in case the original/desired one is no more available,<br>
right?<br>
<br>
If that is correct, how about changing the scheduling of delete operation to use the same logic as create operations, that is pick any of the<br>
available hosts, rather than the one which created a volume in the first place (for backends where that is possible, of course)?<br>
<br>
Thanks!<br>
Arne<br>
<br>
—<br>
<span><font color="#888888">Arne Wiebalck<br>
CERN IT<br>
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<br>
-- <br>
<div>Duncan Thomas</div>
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