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RE: [Xen-users] Re: Differences in performance between file and LVMbased images.


  • To: <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: "JHJE (Jan Holst Jensen)" <jhje@xxxxxxxxxxxxxxx>
  • Date: Wed, 23 Aug 2006 20:54:36 +0200
  • Delivery-date: Wed, 23 Aug 2006 11:55:25 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: AcbG1Xk83YDNF6hpShyEYS/o98c33wAD0qxA
  • Thread-topic: [Xen-users] Re: Differences in performance between file and LVMbased images.

>  Now that I have given it some thought, it seems to me that 
> there's going to be some performance issues with files, and 
> it might even be severe. For each seek, the control has to go 

FWIW I started out using file-backed domUs and had really bad
performance in dom0(!). I saw huge memory consumption and much activity
in dom0 and my understanding is that dom0 was spending an awful lot of
time managing file cache for all the open backing files for the various
domUs. dom0 was quite some time responding when I wanted to log in to it
so that's how I noticed. This was with 5 domUs with low I/O load.

I switched to LVM and has had good performance since then. This was on
Xen 2.0.6 - never tried file-backing in Xen 3.

Cheers
-- Jan Holst Jensen, Novo Nordisk A/S, Denmark

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