Subject: Re: Disk scheduling policy (Re: NEW_BUFQ_STRATEGY)
To: None <tls@rek.tjls.com>
From: Jason Thorpe <thorpej@wasabisystems.com>
List: tech-perform
Date: 12/01/2003 17:08:49
--Apple-Mail-21--321667347
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset=US-ASCII; format=flowed


On Dec 1, 2003, at 4:23 PM, Thor Lancelot Simon wrote:

> Well, I have yet to encounter one that randomly shuffles blocks
> such that sorting in order of increasing block number would be
> _harmful_.  Indeed, since we can see more information about future
> requests than the disk can, it's not clear to me why the elevator
> sort is not highly beneficial.

Well, I certainly agree that elevator sort is not really *harmful*, so 
long as doing it doesn't defeat any queueing tricks that the disk is 
trying to do.  (This all gets really spooky when your "disk" is really 
a disk array with some huge chunk of cache memory in front of it.)

         -- Jason R. Thorpe <thorpej@wasabisystems.com>


--Apple-Mail-21--321667347
content-type: application/pgp-signature; x-mac-type=70674453;
	name=PGP.sig
content-description: This is a digitally signed message part
content-disposition: inline; filename=PGP.sig
content-transfer-encoding: 7bit

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.3 (Darwin)

iD8DBQE/y+YhOpVKkaBm8XkRAvcnAJwLGWFOPpcjotouoP94eHGOFfThAgCePJLg
JZQoGjHspHbo0tzB9I6/AWY=
=Iz4m
-----END PGP SIGNATURE-----

--Apple-Mail-21--321667347--