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Re: [libvirt] [PATCH v2 2/7] conf: Introduce new XML tag "mode" for disk source



On 19/07/13 00:09, Daniel P. Berrange wrote:
On Thu, Jul 18, 2013 at 11:02:37AM -0400, John Ferlan wrote:
From: Osier Yang <jyang redhat com>

There are two ways to use a iSCSI LUN as disk source for qemu.

* The LUN's path as it shows up on host, e.g.
   /dev/disk/by-path/ip-$ip:3260-iscsi-$iqn-fc18:iscsi.iscsi0-lun-1

* The libiscsi URI, e.g.
   iscsi://demo.org:6000/iqn.1992-01.com.example/1

For a "volume" type disk, if the specified "pool" is of iscsi
type, we should support to use the LUN in either of above 2 ways.
That's why to introduce a new XML tag "mode" for the disk source
(libvirt should support iscsi pool with libiscsi, but it's another
new feature, which should be done later).

The "mode" can be either of "host" or "uri". Use "host" to indicate
use of the LUN with the path as it shows up on host. Use "uri" to
indicate to use it with the libiscsi URI (future patches may support
to use network type libvirt storage too, e.g. Ceph, that's why to use
a more general name "uri").
I'm thinking that the mode is really describing the way in which
QEMU uses the iSCSI LUN. Either it access it via the host, or it
accesses it directly.   The fact that the direct access mode has
a cli arg encoded as an URI is really an implementation detail of
current QEMU cli syntax.

yes.


So I'd suggest the "mode" accept either "host" or "direct" instead
of "host" or "uri".

agreed. i was not that sure about the name "uri" when making the
patches actually, "direct" sounds better to me.



Daniel


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