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Re: [Xen-users] MSSQL and Xen performance

On Fri, May 8, 2009 at 4:30 AM, Chris Black <chrisb@xxxxxxxxxxxxxxxxxx> wrote:
> Hello,
> I am working on a xen platform and need to create an MSSQL server. My
> consultant who is doing the installation and setup is refusing to install on
> XEN because he says it will cause to much lag and performance issues with
> the system.

At this point I would ask "how much trust you put in your consultant"? :P

As Nathan pointed out, performance would depend on lots of things. In
short, a virtualized environment would impose some performance
penalty. How much the penalty is, depends on your setup. For Linux PV
guests with LVM-backed device, the penalty is very litlle.

For Windows HVM guests, the penalty could be HUGE. That's because you
get penalty from both CPU and disk/network I/O. To increase
performance you can use PV Drivers (like James Harper's GPLPV) which
would reduce I/O performance penalty.

Note that the same thing generally applies to other virtualization
technology as well (Vmware, virtualbox, etc). You need specialized
driver (or "guest additions") to reduce I/O performance penalty.

> Has anyone done an MSSQL+Xen install before and have you experienced any
> major performance problems? Would the community at large recommend a setup
> like this?

I have several Windows 2003 HVM + GPLPV, LVM-backed storage, with
MSSQL Express. They're lightly-loaded though.



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