[CentOS] "near native" performance with xen?

Ross S. W. Walker rwalker at medallion.com
Mon Aug 6 19:17:03 UTC 2007


> -----Original Message-----
> From: centos-bounces at centos.org 
> [mailto:centos-bounces at centos.org] On Behalf Of Johnn Tan
> Sent: Monday, August 06, 2007 2:56 PM
> To: CentOS mailing list
> Subject: [CentOS] "near native" performance with xen?
> 
> Just wondering if there was a howto or other URL that 
> explains what is needed to achieve "near native" performance 
> on a xen domU -- for this purpose, I am thinking about a 
> single domU running on a physical server, in comparison to 
> that same physical server running the same kernel but 
> non-xenified.
> 
> For instance, using a physical partition for VBD v. using a 
> file-backed one is one of the more obvious ones. Assigning 
> all the VCPUs. And as much RAM as you can get away with 
> (maybe leaving the dom0 with 512MB).
> 
> But are there others? Since I'm doing paravirtualization, I 
> assume I don't need to turn on VT in the BIOS? What about 
> 32-bit v. 64-bit OS, for the dom0 and for the domU? (I'll be 
> using CentOS-5.) Anything else?

You don't need to allocate all the CPUs if the app running in
the domU doesn't need that horse power, same goes for the
memory.

Where you want to concentrate on is storage and network.

Of course you need physical volumes but look for a storage
solution that will also run as direct to disk as possible,
maybe something based on the newer SATA/SAS where the RAID
logic is built into the enclosure and a plain SATA/SAS
card is in the server which can be actively shared between
multiple domUs.

If that is out of your budget then use some type of hardware
RAID for your volumes to get rid of any use of software RAID
in dom0 for guest storage.

Same goes for the network side of things. Install the latest
PV drivers in the domUs to get the latest advances.

-Ross

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