From: Paolo Bonzini <pbonzini@redhat.com>
To: dlaor@redhat.com
Cc: kwolf@redhat.com, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>,
qemu-devel@nongnu.org, fujita.tomonori@lab.ntt.co.jp,
Orit Wasserman <owasserm@redhat.com>,
Ronnie Sahlberg <ronniesahlberg@gmail.com>,
hch@lst.de
Subject: Re: [Qemu-devel] [PATCH] This patch adds a new block driver : iSCSI
Date: Thu, 15 Sep 2011 11:11:34 +0200 [thread overview]
Message-ID: <4E71C146.6070406@redhat.com> (raw)
In-Reply-To: <4E71BBE3.5000207@redhat.com>
On 09/15/2011 10:48 AM, Dor Laor wrote:
>> We need the same patch for NBD, so I wouldn't bother with the
>> synchronous flush.
>
> It seems to me that using a qemu external initiator/target pairs like
> Orit's original design in
> http://wiki.qemu.org/Features/LiveBlockMigration#ISCSI_for_non_shared_storage
> would be a simpler (in terms of qemu code..) and flexible solution.
Yes, it would be simpler for QEMU because everything is done outside.
However, iSCSI is a complex protocol and a complex suite of tools. With
a simpler set of tools such as qemu-nbd/nbd, you can for example tunnel
data over the libvirt connection. Possibly with encryption. Also, with
iSCSI you're tied to raw, while qemu-nbd lets you use qcow2.
iSCSI could be a better choice if everything in the QEMU block layer was
done in terms of SCSI. However, we're a far cry from that.
> I agree that embedding the iscsi initiation in qemu can simplify the end
> user life but since this scenario is expected to be used by higher level
> software it's not relevant here. The risk is to have to maintain more
> code that won't be as general as the tgtd/lio solutions out there.
I'm not sure I understand. You say "embedding the iSCSI initiator in
qemu can simplify the end user life" but "the risk is to have to
maintain [another iSCSI target]". I don't think anybody proposed adding
an iSCSI target to QEMU (in fact tcm_vhost would even let you use lio
instead of QEMU's SCSI target code!). Only an iSCSI initiator which is
not much code because it's just a wrapper for libiscsi.
In general, I'm not sure that libiscsi (instead of the in-kernel iSCSI
initiator) is by definition a bad choice in high-end set-ups. If you
want to do SCSI passthrough, it's likely better to use libiscsi rather
than using the in-kernel initiator together with scsi-generic
(scsi-generic sucks; bsg is better but also a useless level of
indirection IMO).
Perhaps Ronnie has rough performance numbers comparing in-kernel iSCSI
with libiscsi?
Paolo
next prev parent reply other threads:[~2011-09-15 9:12 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-10 4:23 [Qemu-devel] [PATCH] Add iSCSI support for QEMU Ronnie Sahlberg
2011-09-10 4:23 ` [Qemu-devel] [PATCH] This patch adds a new block driver : iSCSI Ronnie Sahlberg
2011-09-12 9:14 ` Stefan Hajnoczi
2011-09-14 14:36 ` Christoph Hellwig
2011-09-14 15:50 ` Stefan Hajnoczi
2011-09-16 15:53 ` Christoph Hellwig
2011-09-17 7:11 ` Stefan Hajnoczi
2011-09-14 22:51 ` ronnie sahlberg
2011-09-15 8:02 ` Daniel P. Berrange
2011-09-15 9:03 ` Kevin Wolf
2011-09-14 23:08 ` ronnie sahlberg
2011-09-15 6:04 ` Paolo Bonzini
2011-09-15 8:48 ` Dor Laor
2011-09-15 9:11 ` Paolo Bonzini [this message]
2011-09-15 11:27 ` ronnie sahlberg
2011-09-15 11:42 ` Dor Laor
2011-09-15 11:46 ` Christoph Hellwig
2011-09-15 12:01 ` Dor Laor
2011-09-15 12:04 ` Paolo Bonzini
2011-09-15 11:58 ` Paolo Bonzini
2011-09-15 12:34 ` Orit Wasserman
2011-09-15 12:58 ` Paolo Bonzini
2011-09-15 16:59 ` Orit Wasserman
2011-09-15 9:44 ` Daniel P. Berrange
2011-09-15 9:10 ` Kevin Wolf
2011-09-15 9:39 ` Paolo Bonzini
2011-09-21 9:48 ` ronnie sahlberg
2011-09-23 9:15 ` Mark Wu
2011-09-23 10:16 ` Paolo Bonzini
2011-09-12 8:56 ` [Qemu-devel] [PATCH] Add iSCSI support for QEMU Kevin Wolf
2011-09-14 12:24 ` Orit Wasserman
2011-09-14 14:33 ` Christoph Hellwig
2011-09-14 14:37 ` Christoph Hellwig
2011-09-14 15:35 ` Stefan Hajnoczi
2011-09-14 15:40 ` Christoph Hellwig
2011-09-14 15:51 ` Stefan Hajnoczi
2011-09-14 16:36 ` Orit Wasserman
2011-09-15 6:06 ` Paolo Bonzini
2011-09-15 9:52 ` Orit Wasserman
2011-09-15 9:55 ` Paolo Bonzini
2011-09-15 10:10 ` Kevin Wolf
2011-09-17 19:08 ` Laurent Vivier
2011-09-18 7:43 ` Paolo Bonzini
2011-09-14 16:37 ` Paolo Bonzini
2011-09-14 22:46 ` ronnie sahlberg
-- strict thread matches above, loose matches on Subject: below --
2011-09-21 9:37 Ronnie Sahlberg
2011-09-21 9:37 ` [Qemu-devel] [PATCH] This patch adds a new block driver : iSCSI Ronnie Sahlberg
2011-09-21 9:45 ` Paolo Bonzini
2011-09-21 9:52 ` ronnie sahlberg
2011-09-27 20:08 ` ronnie sahlberg
2011-09-28 5:54 ` Paolo Bonzini
2011-09-29 6:54 ` Stefan Hajnoczi
2011-10-09 20:46 ` ronnie sahlberg
2011-10-13 9:46 ` ronnie sahlberg
2011-10-13 9:48 ` Paolo Bonzini
2011-10-13 9:54 ` Stefan Hajnoczi
2011-10-13 10:01 ` Daniel P. Berrange
2011-10-13 10:55 ` Daniel P. Berrange
2011-10-13 10:52 ` Kevin Wolf
2011-10-24 13:33 ` Kevin Wolf
2011-10-25 8:04 ` ronnie sahlberg
2011-10-25 8:17 ` Kevin Wolf
2011-10-25 8:23 ` ronnie sahlberg
2011-10-25 8:46 ` Kevin Wolf
2011-10-28 10:46 ` Zhi Yong Wu
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