Messages in this thread | | | Subject | Re: [RFC PATCH 35/35] Add Xen virtual block device driver. | From | Alan Cox <> | Date | Fri, 24 Mar 2006 15:55:27 +0000 |
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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 > > In fact, SCSI should make a few things easier, because the notion of > host+bus topology is already present, and notion of messaging is already > present, so you don't have to recreate that in a Xen block device > infrastructure.
Those are the easy bits.
> > are also always full of bits people got wrong, often critical bits like > > tagged queues and error sequences - things that break your journalled > > file system. > > This I'll grant you.
And every one you get wrong is a corruptor....
Alan
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