On Wed, Jun 22, 2016 at 07:03:46AM -0400, John Ferlan wrote:
On 06/17/2016 11:16 AM, Ján Tomko wrote:
On Thu, Jun 16, 2016 at 07:44:05AM -0400, John Ferlan wrote:
On 06/16/2016 06:03 AM, Ján Tomko wrote:
On Wed, Jun 15, 2016 at 06:45:59PM -0400, John Ferlan wrote:
On 06/15/2016 01:19 PM, Ján Tomko wrote:
Regression introduced by commit 71b803a for [1] that prevents
starting up
a logical pool created with <source><device path=''></source>
after it has been moved to a different physical volume.
Is there a bug for this? XML examples?
Is an empty source device path string a valid value? Reading
http://libvirt.org/formatstorage.html doesn't give me that impression.
I meant any pool with a <device> specified, not an empty path.
But the patch is specifically targeted at removing the _logical pool
check. So the question is, is it "legal" for a logical pool to "start"
with an empty string as a source device path? Secondarily I'm curious
what's the use case of that?
I do not know what happens with an empty string.
<source><device path=''></source> was not an exact snippet,
just a hint that there is a device path specified.
If you create a pool like this:
<pool type='logical'>
<name>vgname</name>
<source>
<device path='/dev/sda4'/>
<name>vgname</name>
As I see things, this more or less lets libvirt "know" that "/dev/sda4"
and "vgname" are associated.
</source>
<target>
<path>/dev/vgname</path>
</target>
</pool>
Then pvmove /dev/sda4 to /dev/sda5, libvirt will refuse that pool
even though <name>vgname</name> is enough to uniquely identify a storage
pool.
As an admin you take this step to pvmove your data from /dev/sda4 to
/dev/sda5.
But then you expect libvirt to know that? Do you expect libvirt to
automagically update the XML to /dev/sda5 during 'build' or 'start'?
The whole point of LVM is abstraction from the lower layers so we
shouldn't ever be checking this.
So it's OK to activate/start a pool where the source device path is
incorrect?
For LVM, the important path is in <source><name>.
But isn't there a 1-to-1 relationship between the VG and the PV? A PV
cannot be in more than one VG, so if you move your PV, then you have to
update your XML to let libvirt know.
Why would it need to know? Apart from pool building, libvirt does not
need the value for anything.
Jan
John
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