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<div class="moz-cite-prefix">On 10/28/2014 02:50 PM, John Griffith
wrote:<br>
</div>
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cite="mid:CA+qL3LVJs2BRUFp=J++NLULXRSRH67MQL9LZcA5psTYPFo6cNg@mail.gmail.com"
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<div class="gmail_quote">On Tue, Oct 28, 2014 at 12:37 PM, Dan
Genin <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:daniel.genin@jhuapl.edu" target="_blank">daniel.genin@jhuapl.edu</a>></span>
wrote:<br>
<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">Great,
thank you, Duncan. I will then proceed with the shared
volume group.<span class=""><font color="#888888"><br>
<br>
Dan</font></span>
<div class="">
<div class="h5"><br>
<br>
On 10/28/2014 02:06 PM, Duncan Thomas wrote:<br>
<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">Cinder
volumes are always (unless you go change the
default) in the<br>
form: volume-<uuid>, and since the string
'volume-' is never a valid<br>
uuid, then I think we can work around nova volumes
fine when we come<br>
to write our tests.<br>
<br>
Sorry for the repeated circling on this, but I think
I'm now happy.<br>
<br>
Thanks<br>
<br>
<br>
<br>
On 28 October 2014 17:53, Dan Genin <<a
moz-do-not-send="true"
href="mailto:daniel.genin@jhuapl.edu"
target="_blank">daniel.genin@jhuapl.edu</a>>
wrote:<br>
<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">On
10/28/2014 11:56 AM, Dean Troyer wrote:<br>
<br>
On Tue, Oct 28, 2014 at 9:27 AM, Dan Genin <<a
moz-do-not-send="true"
href="mailto:daniel.genin@jhuapl.edu"
target="_blank">daniel.genin@jhuapl.edu</a>>
wrote:<br>
<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">So
this brings us back to the original proposal of
having separate backing<br>
files for Cinder and Nova which Dean thought
might take too much space.<br>
</blockquote>
<br>
Between Cinder, Nova and Swift (and Ceph, etc)
everybody wants some loopback<br>
disk images. DevStack's Swift and Ceph
configurations assume loopback<br>
devices and do no sharing.<br>
<br>
<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">Duncan,
could you please elaborate on the pain a single
volume group is<br>
likely to cause for Cinder? Is it a show
stopper?<br>
</blockquote>
<br>
Back in the day, DevStack was built to configure
Cinder (and Nova Volume<br>
before that) to use a specific existing volume
group (VOLUME_GROUP_NAME) or<br>
create a loopback file if necessary. With the
help of VOLUME_NAME_PREFIX<br>
and volume_name_template DevStack knew which
logical volumes belong to<br>
Cinder and could Do The Right Thing.<br>
<br>
With three loopback files being created, all
wanting larger and larger<br>
defaults, adding a fourth becomes Just One More
Thing. If Nova's use of LVM<br>
is similar enough to Cinder's (uses deterministic
naming for the LVs) I'm<br>
betting we could make it work.<br>
<br>
dt<br>
<br>
Nova's disk names are of the form
<instance-uuid>_<disk_type>. So<br>
deterministic but, unfortunately, not necessarily
predictable. It sounds<br>
like Duncan is saying that Cinder needs a fixed
prefix for testing its<br>
functionality. I will be honest, I am not
optimistic about convincing Nova<br>
to change their disk naming scheme for the sake of
LVM testing. Far more<br>
important changes have lingered for months and
sometimes longer.<br>
<br>
It sounds like you are concerned about two issues
with regard to the<br>
separate volume groups approach: 1) potential loop
device shortage and 2)<br>
growing space demand. The second issue, it seems
to me, will arise no matter<br>
which of the two solutions we choose. More space
will be required for<br>
testing Nova's LVM functionality one way or
another, although, using a<br>
shared volume group would permit a more efficient
use of the available<br>
space. The first issue is, indeed, a direct
consequence of the choice to use<br>
distinct volume groups. However, the number of
available loop devices can be<br>
increased by passing the appropriate boot
parameter to the kernel, which can<br>
be easy or hard depending on how the test VMs are
spun up.<br>
<br>
I am not saying that we should necessarily go the
way of separate volume<br>
groups but, assuming for the moment that changing
Nova's disk naming scheme<br>
is not an option, we need to figure out what will
bring the least amount of<br>
pain forcing Cinder tests to work around Nova
volumes or create separate<br>
volume groups.<br>
<br>
Let me know what you think.<br>
Dan<br>
<br>
<br>
--<br>
<br>
Dean Troyer<br>
<a moz-do-not-send="true"
href="mailto:dtroyer@gmail.com" target="_blank">dtroyer@gmail.com</a><br>
<br>
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<div class="gmail_extra">Noticed my response never posted....
think there's something up with my mail client, so if you get
this a few more times forgive me :)</div>
<div class="gmail_extra"><br>
</div>
<div class="gmail_extra">But....</div>
<div class="gmail_extra">
<pre style="margin-top:0px;margin-bottom:0px;padding:0px;font-family:inherit;font-size:13px;font-stretch:inherit;line-height:16.25px;white-space:pre-wrap;word-wrap:break-word;color:rgb(31,31,31)">The idea of sharing a VG
between Nova and Cinder is only relevant in an all in one deployment
anyway, it's a specific edge case for testing. It certainly (IMHO) does
not warrant any changes in Nova and Cinder. Also keep in mind that at
some point (I think we're already there) we need to consider whether our
default gating and setup can continue to be done on a single node
anyway.
</pre>
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</blockquote>
Agree.<br>
<blockquote
cite="mid:CA+qL3LVJs2BRUFp=J++NLULXRSRH67MQL9LZcA5psTYPFo6cNg@mail.gmail.com"
type="cite">
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<div class="gmail_extra">
<pre style="margin-top:0px;margin-bottom:0px;padding:0px;font-family:inherit;font-size:13px;font-stretch:inherit;line-height:16.25px;white-space:pre-wrap;word-wrap:break-word;color:rgb(31,31,31)">
The answer to this seems relatively simple to me, Dean pointed out just
add a loopback device specifically for Nova LVM testing and move on.</pre>
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Dean is actually for using a shared VG to conserve space and loop
devices.<br>
<br>
Dan<br>
<blockquote
cite="mid:CA+qL3LVJs2BRUFp=J++NLULXRSRH67MQL9LZcA5psTYPFo6cNg@mail.gmail.com"
type="cite">
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