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From: Vadim Rozenfeld <vrozenfe@redhat.com>
Date: Tue, 8 Jan 2013 12:21:44 +0200
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Subject: Re: [Qemu-devel] Windows and I/O size
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To: Peter Lieven <pl@dlhnet.de>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, ronnie sahlberg <ronniesahlberg@gmail.com>

On Tuesday, January 08, 2013 12:09:11 PM Peter Lieven wrote:
> Am 08.01.2013 um 10:29 schrieb Vadim Rozenfeld <vrozenfe@redhat.com>:
> > On Tuesday, January 08, 2013 10:53:44 AM Peter Lieven wrote:
> >> Am 08.01.2013 um 09:50 schrieb Vadim Rozenfeld <vrozenfe@redhat.com>:
> >>> On Tuesday, January 08, 2013 10:16:48 AM Peter Lieven wrote:
> >>>> Hi all,
> >>>> 
> >>>> I came across the fact that Windows seems to requests greater 64KB
> >>>> into pieces leading to a lot of IOPs on the storage side.
> >>>> 
> >>>> Can anyone imagine of a way to merge them before sending them to e.g.
> >>>> an iSCSI Storage? 64KB I/O Size is not optimal when e.g. large
> >>>> sequential operations with an iSCSI target.
> >>>> 
> >>>> Thank you,
> >>>> Peter
> >>> 
> >>> Hi Peter.
> >>> Is it viostor? Which version? The most recent one is able to handle
> >>> 256K blocks.
> >> 
> >> Not the recent. I will try 0.1.49 now.
> >> 
> >> 256KB is still not that much but definitely better than 64KB. are this
> >> windows limits?
> > 
> > not exactly. it came from the driver itself. actually, with indirect
> > buffer support in virtio the sky is the limit.
> 
> is indirect buffering supported on all windows platforms?
yes.
btw, forgot to mention that vioscsi doesn't have this feature yet. 
> 
> Peter
> 
> >> I have found docs in the net that windows splits up everything into 64kB
> >> requests. Is this info old?
> >> 
> >> thank you,
> >> Peter
> >> 
> >>> Best regards,
> >>> Vadim.