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

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Ligesh
> Sent: 23 August 2006 16:49
> To: Petersson, Mats
> Cc: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] Re: Differences in performance between 
> file and LVM based images.
> 
> 
> "Petersson, Mats" <Mats.Petersson@xxxxxxx> said.
> > > 
> > >  Hello folks,
> > > 
> > >  How much is the performance penalty if you use a file 
> > > instead of an LVM? Has there been any benchmarks on this?
> > 
> > I haven't done any benchmarks, but I would like to point out that it
> > would depend VERY MUCH on exactly what the application 
> running on top of
> > the VM is. 
> > 
> 
>  And how will that depend on the application?  Disk access is 
> pretty much about the read/write/seek times right? Do you 
> mean that there are some applications that will be faster on 
> file based disks, and some others that faster on LVMs? 

Probably yes. How much? Don't know. 

But I was more referring to the fact that different applications do
different things to disks in the first place, so the application
behaviour may depend on "seek time" or "write time" or "read time" in
different proportions [1], so just using "hdparm" or something like that
wouldn't really be a useful measure of how some particular application
will perform on any given setup. 

If you do make some measurements to compare different setups
(preferrably with some different benchmarks that all depend on disk
performance), I'd be very interested to see the results. 

Note also that there is a new interface for file-based IO called blktap,
which I believe is a bit better than the old style block device backend
driver... 

--
Mats 
> 
>  Thanks a lot for your time.
> 
> --
> :: Ligesh :: http://ligesh.com 
> 
> 
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