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From: Vadim Rozenfeld <vrozenfe@redhat.com>
Date: Tue, 8 Jan 2013 11:29:59 +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 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.  

> 
> 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.