PE R805/2950 + MD3000i + CentOS 5.2 + Xen 3.3 + open-iscsi + dm-multipath/RDAC

[Adrian Schmitz]

Hello,

 

I have some poweredge R805s and 2950s that I've been using as virtual
hosts under CentOS 5.2 with the included versions of Xen (3.0),
open-iscsi, and dm-multipath. The Xen DomU disk images are stored in
virtual disks on an attached MD3000i. Overall, I'd say it's worked very
well for us. 

 

One complaint I've had with this setup is that we can't use the GPLPV
accelerated drivers on our windows guests since GPLPV doesn't support
Xen earlier than 3.1 or 3.2 (I can't remember.. but it definitely
doesn't work on the 3.0 included in CentOS 5.2.) So, I've set out to
upgrade to Xen 3.3.0..

 

I've successfully built and installed Xen 3.3.0 from the xensource
tarball along with its included 2.6.18.8 Dom0 kernel. No problem..

 

I then discovered that the version of the open-iscsi userland utils
included in CentOS disagreed with the modules that built with the 2.6.18
Dom0 kernel (causing a kernel panic during iscsi login), so I built and
installed new userland utils and matching kernel modules from the
open-iscsi tarball. No problem..

 

Finally, I tried to configure dm-multipath for my virtual disks, and
realized that the dm RDAC module was missing from the new kernel I
built. After a bit of Googling, it looks to me like the RDAC module is
something specific to the redhat distribution kernels (please correct me
if I'm wrong). So, now I'm wondering where to go from here.. Some of the
posts I've come across hint at a kernel patch for RDAC support, but I
can't seem to find the patch for download. 

 

So that's the story.. here are my questions:

1)      Is there a way to add RDAC support for my MD3000i to my 2.6.18.8
dom0 kernel?

2)      If someone else has experience with a setup like this, am I
wasting my time? Is GPLPV  and the upgrade to Xen 3.3 from 3.0 not worth
the effort?

 

On a side-note, if anyone has experience with KVM virtualization on
CentOS in an application like this, I'd be interested in any feedback
you can provide. I gave it a short try before I started with Xen 3.0 and
it worked okay, although my windows guest performance seemed better out
of the box on Xen than it did with KVM.. my guest CPU usage always
seemed unreasonably high under KVM, although I could've been missing
something simple.

 

Anyway.. sorry for the long post.. Any advice is greatly appreciated.

 

-Adrian

 

 

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