[libvirt] [PATCH]: vgscan before doing logical pool discovery
Chris Lalancette
clalance at redhat.com
Wed Nov 5 11:44:55 UTC 2008
Daniel P. Berrange wrote:
> On Tue, Nov 04, 2008 at 06:32:37PM +0100, Chris Lalancette wrote:
>> Assume that you have an iSCSI target available, and on that iSCSI target 1 LUN
>> is exported. On that 1 LUN, you have an LVM volume group (say, myvg), with 2
>> logical volumes (say, lv1 and lv2). Now you execute the following sequence of
>> commands:
>>
>> 1) virsh define iscsi_pool.xml
>> 2) virsh start iscsi_pool
>> 3) virsh find-storage-pool-sources-as logical
>>
>> With that sequence, you would expect step 3) to return XML similar to:
>>
>> <sources><source><name>myvg</name><device path='/dev/sdb'/></source></sources>
>>
>> However, what you instead get is: <sources/>. That's because if you just try to
>> do storage pool discovery on a logical pool without ever touching the logical
>> pool in any fashion, pvs (what we use to do discovery) doesn't return anything.
>> If you touch the logical volume group at all (say, with vgscan), they then
>> suddenly appear. To make sure we see all of the potential volume groups when
>> doing pool discovery, make sure to run vgscan before we run pvs. With this
>> patch in place, logical discovery just does the right thing.
>
> ACK, this makes total sense.
Thanks, committed.
--
Chris Lalancette
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