Re: [Xen-users] Xen Disk I/O performance vs native performance

["Mitch Kelly" <mitchkelly@xxxxxxxxxxxxxx>]

DL380 Gen3 HP SmartArray 5i 64mb.

Raid 5 Array:  4x 36Gb 10k Ultra320:
/dev/cciss/c0d0:
Timing cached reads:   784 MB in  2.00 seconds = 392.13 MB/sec
Timing buffered disk reads:  240 MB in  3.01 seconds =  79.78 MB/sec

Raid 1 Array: 2x 146gb 10k Ultra320:
/dev/cciss/c0d1:
Timing cached reads:   850 MB in  2.00 seconds = 424.73 MB/sec
Timing buffered disk reads:  210 MB in  3.00 seconds =  69.97 MB/sec

----- Original Message ----- 
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
To: "Mitch Kelly" <mitchkelly@xxxxxxxxxxxxxx>; "Sami Dalouche" 
<skoobi@xxxxxxx>; "Javier Guerra" <javier@xxxxxxxxxxx>
Cc: "Xen Users" <xen-users@xxxxxxxxxxxxxxxxxxx>
Sent: Saturday, January 26, 2008 2:13 PM
Subject: RE: [Xen-users] Xen Disk I/O performance vs native performance


> Subject: Re: [Xen-users] Xen Disk I/O performance vs native
performance
> Im curious, What PC do you have? Im running a Compaq DL380 and get
crap
> Profomace at the moment.
What sort of DL380, and what sort of disks?

I've got a DL385 with 146G 10K 2.5" SAS disks on a HP RAID controller,
and hdparm -tT /dev/cciss/c0d0 gives me around 900MB/sec for cached
reads, and around 235MB/sec for buffered reads.

hdparm -tT on an lv used in DomU, with hdparm being run from Dom0 gives
me about the same for cached reads, but only 60MB/sec for buffered
reads.

hdparm -tT on the same lv under DomU gives me 35-50MB/sec.

So I'm getting a pretty drastic performance hit from lvm (never noticed
that before... guess I should look into it... maybe it's an artefact of
hdparm) and a small hit from xen blockfront/back.

James


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