On 06/25/2012 10:14 AM, Deepak C Shetty wrote:
On 06/25/2012 07:47 AM, Shu Ming wrote:
On 2012-6-25 10:10, Andrew Cathrow wrote:

----- Original Message -----
From: "Andy Grover" <agro...@redhat.com>
To: "Shu Ming" <shum...@linux.vnet.ibm.com>
Cc: libstoragemgmt-de...@lists.sourceforge.net,
engine-de...@ovirt.org, "VDSM Project Development"
Sent: Sunday, June 24, 2012 10:05:45 PM
Subject: Re: [vdsm] [Engine-devel] RFC: Writeup on
VDSM-libstoragemgmt integration

On 06/24/2012 07:28 AM, Shu Ming wrote:
On 2012-6-23 20:40, Itamar Heim wrote:
On 06/23/2012 03:09 AM, Andy Grover wrote:
On 06/22/2012 04:46 PM, Itamar Heim wrote:
On 06/23/2012 02:31 AM, Andy Grover wrote:
On 06/18/2012 01:15 PM, Saggi Mizrahi wrote:
Also, there is no mention on credentials in any part of the
How does VDSM or the host get access to actually modify the
array? Who holds the creds for that and how? How does the user
this up?
It seems to me more natural to have the oVirt-engine use
directly to allocate and export a volume on the storage array,
pass this info to the vdsm on the node creating the vm. This
Saggi's question about creds -- vdsm never needs array
creds, it only gets handed the params needed to connect and use
block device (ip, iqn, chap, lun).

Is this usage model made difficult or impossible by the current
what about live snapshots?
I'm not a virt guy, so extreme handwaving:

vm X uses luns 1& 2

engine -> vdsm "pause vm X"
that's pausing the VM. live snapshot isn't supposed to do so.
Tough we don't expect to do a pausing operation to the VM when live
snaphot is undergoing, the VM should be blocked on the access to
specific luns for a while. The blocking time should be very short
avoid the storage IO time out in the VM.
OK my mistake, we don't pause the VM during live snapshot, we block
access to the luns while snapshotting. Does this keep live snapshots
working and mean ovirt-engine can use libsm to config the storage
instead of vdsm?

Because that was really my main question, should we be talking about
engine-libstoragemgmt integration rather than vdsm-libstoragemgmt
for snapshotting wouldn't we want VDSM to handle the coordination of
the various atomic functions?

I think VDSM-libstoragemgmt will let the storage array itself to make
the snapshot and handle the coordination of the various atomic
functions. VDSM should be blocked on the following access to the
specific luns which are under snapshotting.

I kind of agree. If snapshot is being done at the array level, then the
array takes care of quiesing the I/O, taking the snapshot and allowing
the I/O, why does VDSM have to worry about anything here, it should all
happen transparently for VDSM, isnt it ?

I may be misssing something, but afaiu you need to ask the guest to perform the quiesce, and i'm sure the storage array can't do that.
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