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Message-ID: <Pine.LNX.4.62.0904141447520.13379@tamago.serverit.net>
Date: Tue, 14 Apr 2009 14:58:11 +0300 (EEST)
From: Szabolcs Szakacsits <szaka@...s-3g.com>
To: Jeff Garzik <jeff@...zik.org>
cc: Avi Kivity <avi@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Alan Cox <alan@...rguk.ukuu.org.uk>,
Grant Grundler <grundler@...gle.com>,
Linux IDE mailing list <linux-ide@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Jens Axboe <jens.axboe@...cle.com>,
Arjan van de Ven <arjan@...radead.org>
Subject: Re: Implementing NVMHCI...
On Tue, 14 Apr 2009, Jeff Garzik wrote:
> Avi Kivity wrote:
> > Jeff Garzik wrote:
> > > Speaking of RMW... in one sense, we have to deal with RMW anyway.
> > > Upcoming ATA hard drives will be configured with a normal 512b sector API
> > > interface, but underlying physical sector size is 1k or 4k.
> > >
> > > The disk performs the RMW for us, but we must be aware of physical sector
> > > size in order to determine proper alignment of on-disk data, to minimize
> > > RMW cycles.
> > >
> >
> > Virtualization has the same issue. OS installers will typically setup the
> > first partition at sector 63, and that means every page-sized block access
> > will be misaligned. Particularly bad when the guest's disk is backed on a
> > regular file.
> >
> > Windows 2008 aligns partitions on a 1MB boundary, IIRC.
>
> Makes a lot of sense...
Since Vista at least the first partition is 2048 sector aligned.
Szaka
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