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Re: [Xen-users] Difference between file and tap:aio

To: Fantu <fantonifabio@xxxxxxxxxx>
Subject: Re: [Xen-users] Difference between file and tap:aio
From: Pasi Kärkkäinen <pasik@xxxxxx>
Date: Fri, 9 Apr 2010 17:24:44 +0300
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On Fri, Apr 09, 2010 at 07:13:22AM -0700, Fantu wrote:
> 
> Someone can explain me good difference between file and tap:aio, pros and
> cons, and also with all possibility with blktap2? Thanks for any response
>

file: uses dom0 kernel page cache, and thus might give better performance than 
phy: or tap:aio:,
but it's also more insecure because of the caching.

tap:aio: uses direct IO, so it bypasses dom0 kernel caches, and works like phy: 
in that sense.

blktap1 provides also other modes than :aio, like: qcow, but those were not 
very stable or fast,
so blktap2 was developed. for blktap1 see: 
http://wiki.xensource.com/xenwiki/blktap .

blktap2 also has vhd image support including snapshots and cloning.
See here: http://wiki.xensource.com/xenwiki/blktap2 .

-- Pasi


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