Re: [libvirt] [PATCH]: vgscan before doing logical pool discovery

[Chris Lalancette <clalance redhat com>]

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