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


  • To: Xen Users <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: Tegger <xen@xxxxxxxxx>
  • Date: Mon, 12 Apr 2010 23:13:40 +0200
  • Delivery-date: Mon, 12 Apr 2010 14:14:53 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>

Would file: really have a better performance than phy: ? I am planing to use a own partition for my Windows HVM Domain, cause in the fact you going to use a Filesystem in a filesystem, so this need more time than only "one" filesystem i think.....



Am 09.04.2010 16:24, schrieb Pasi Kärkkäinen:
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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