From: Rusty Russell <rusty@rustcorp.com.au>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: xen-devel@lists.xensource.com, Jeff Garzik <jeff@garzik.org>,
SCSI Mailing List <linux-scsi@vger.kernel.org>,
virtualization@lists.osdl.org, linux-kernel@vger.kernel.org,
Chris Wright <chrisw@sous-sol.org>,
Ian Pratt <ian.pratt@xensource.com>
Subject: Re: [RFC PATCH 35/35] Add Xen virtual block device driver.
Date: Sat, 25 Mar 2006 21:03:11 +1100 [thread overview]
Message-ID: <1143280992.8228.12.camel@localhost.localdomain> (raw)
In-Reply-To: <1143215728.18986.15.camel@localhost.localdomain>
On Fri, 2006-03-24 at 15:55 +0000, Alan Cox wrote:
> On Gwe, 2006-03-24 at 07:38 -0500, Jeff Garzik wrote:
> > > A pure SCSI abstraction doesn't allow for shared head scheduling which
> > > you will need to scale Xen sanely on typical PC boxes.
> >
> > Not true at all. If you can do it with a block device, you can do it
> > with a SCSI block device.
>
> I don't believe this is true. The complexity of expressing sequences of
> command ordering between virtual machines acting in a co-operative but
> secure manner isn't as far as I can see expressable sanely in SCSI TCQ
I thought usb_scsi taught us that SCSI was overkill for a block
abstraction? I have a much simpler Xen block-device implementation
which seems to perform OK, and is a lot less LOC than the in-tree one,
so I don't think the "SCSI would be better than what's there" (while
possibly true) is valid.
Cheers!
Rusty.
--
ccontrol: http://ozlabs.org/~rusty/ccontrol
next prev parent reply other threads:[~2006-03-25 10:03 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <A95E2296287EAD4EB592B5DEEFCE0E9D4B9E8A@liverpoolst.ad.cl.cam.ac.uk>
2006-03-22 23:09 ` [RFC PATCH 35/35] Add Xen virtual block device driver Jeff Garzik
2006-03-24 12:17 ` Alan Cox
2006-03-24 12:38 ` Jeff Garzik
2006-03-24 13:37 ` Jeff Garzik
2006-03-24 13:40 ` Arjan van de Ven
2006-03-24 13:50 ` Jeff Garzik
2006-03-24 15:33 ` Dave C Boutcher
2006-03-24 19:04 ` Mike Christie
2006-03-24 19:19 ` Dave C Boutcher
2006-03-25 0:32 ` FUJITA Tomonori
2006-03-25 0:47 ` Roland Dreier
2006-03-24 15:55 ` Alan Cox
2006-03-25 10:03 ` Rusty Russell [this message]
2006-03-27 10:14 ` Peter Chubb
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