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Date: Wed, 04 Aug 2010 12:53:23 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with
	Linux 2.6.35?
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To: Avi Kivity <avi@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>, kvm@vger.kernel.org, "Richard W.M. Jones" <rjones@redhat.com>, qemu-devel@nongnu.org, Alexander Graf <agraf@suse.de>, Paolo Bonzini <pbonzini@redhat.com>

On 08/04/2010 12:37 PM, Avi Kivity wrote:
>  On 08/04/2010 08:27 PM, Anthony Liguori wrote:
>> On 08/04/2010 12:19 PM, Avi Kivity wrote:
>>>  On 08/04/2010 08:01 PM, Paolo Bonzini wrote:
>>>>
>>>> That's another story and I totally agree here, but not reusing 
>>>> /dev/sd* is not intrinsic in the design of virtio-blk (and one 
>>>> thing that Windows gets right; everything is SCSI, period).
>>>>
>>>
>>> I don't really get why everything must be SCSI.  Everything must 
>>> support read, write, a few other commands, and a large set of 
>>> optional commands.  But why map them all to SCSI?  What's the magic?
>>
>> Because that's what real hardware with only a few rare exceptions.
>>
>
> I thought that IDE was emulated as SCSI even when it wasn't.  But I 
> guess now with SATA you're right.

IDE -> EIDE -> ATA -> SATA

ATA can encapsulate SCSI commands via ATAPI which gives you the ability 
to have ATA based CD-ROMs among other things.

I don't believe that SATA actually uses SCSI commands for read/write 
operations but I think Linux exposes SATA drivers as SCSI anyway.

Regards,

Anthony Liguori