Best resources/forums for Xen HA setup?

Thu Sep 25 21:48:54 BST 2008

Thanks Randy, we have segregated our iSCSI traffic it only shares 
bandwidth with WAN traffic on our fiber links between locations when the 
units replicate data (and we can throttle that).  The iSCSI backbone also 
has redundant switches and each host connected has 2 teamed GB NICs.

My biggest question is connections and LAN bandwidth, we usually have 
between 1000 and 1500 connections on each of our physical cluster nodes 
during school hours and I am concerned that the virtual servers on any Xen 
host will now be sharing the bandwidth of a single team of NICs and may be 
sluggish, granted I haven't done any concrete bandwidth studies.  We also 
use Backup Express which pulls the data from each host over the LAN and 
backs up to our FC attached tape library so again the LAN bandwidth is an 
issue, however, since all this data is flowing through 1 backup server I 
guess the backup server would be a bottle neck before anything else.  So 
much for KISS huh!

Anyone else have any problems with performance of virtual hosts on iSCSI?

Thanks.

T2

"Randy Grein" <RGrein at tpchd.org> 
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09/25/2008 04:15 PM
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RE: Best resources/forums for Xen HA setup?

I have to say that after 6 months with vmware ESX version 3.5, I believe) 
using iSCSI SAN for storage I'm not impressed. It works OK when it works, 
and it is possible to run virtual clients across our metro fiber - but any 
LAN hickup causes problems. As you're early in the process plan it out. 
Use the KISS principal, avoid VLAN complications (especially dynamic VLAN 
assignments) and if at all possible use a separate switch environment for 
iSCSI traffic. Check with HP and Lefthand ahead of time for iSCSI support.

Randy Grein
Sr. Network Engineer

>>> <TJohnson at lancaster.wnyric.org> 9/25/2008 12:30 PM >>>
I have to admit that I was not thinking of this approach but our district 
wants to get virtualization in but we were short on similar hardware to 
create a resource pool for our virtualization environment but we do have 2 

new servers that were meant to be used for a 2 node physical OES2 Linux 
cluster The original post made me think that a virtual cluster would be a 
perfect way to get virtuialization in the door.

So if I can talk my boss into going this route than this is what we are 
planning:

XenServer 5.0.0 Enterprise for virtualization

2 virtual hosts - HP DL360G5 , 2 quad core 3.2 GHZ Intel processors, 8 GB 
of RAM (hopefully increased to 32GB), 4 NICs

Lefthand iSCSI SAN

2 Node OES2/SELS10 NCS cluster (all 64 bit)

Can anyone comment on Xenserver, NCS in a virtual environment or any other 

suggestions and/or pitfalls with this type of plan?

As always I will eagerly await the wisdom of the group.

Thanks.

T2

"Kevin Parris" <KPARRIS at ed.sc.gov> 
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09/24/2008 10:22 AM
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linux-poweredge at dell.com 
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RE: Best resources/forums for Xen HA setup?

Not opposite at all, but complementary.  Create virtual servers on 
separate physical hosts, and cluster the virtual.

Using a virtual server is not JUST for running multiple on a single 
physical box.  You gain ease of mobility - if your virtual server workload 

outgrows the original physical host, all you have to do is shut it down, 
copy the guest fileset to a more powerful physical host, and start it up 
(generally) - viola! you have migrated the service to new hardware without 

having to re-install the OS and applications.

I'm trying to avoid running anything on "actual physical system" if there 
isn't some serious reason why the function can't work in a virtual guest. 
The ease of mobility plus the backup/recover process is so much better.

>>> "Brian Hatchell" <hatchellb at vvc.edu> 09/23/08 9:48 PM >>>
Correct me if I am wrong, why would you virtualize a HA cluster? 
Clustering is distributing resources through physical servers. 
Virtualization is running multiple OSes on one Physical server.  Aren't 
they opposite philosophies?

Brian Hatchell
Network Manager
Sent from my Mobile Device, typos are common!

-----Original Message-----
From: Paul Gear <paul at gear.dyndns.org>
Sent: Tuesday, September 23, 2008 5:34 PM
To: novell at netlab1.usu.edu <novell at netlab1.usu.edu>
Cc: linux-poweredge at dell.com <linux-poweredge at dell.com>
Subject: Best resources/forums for Xen HA setup?

Hi folks,

I've been working my way through Novell's "conquering the HASF" document, 
which details the setup of a Heartbeat2/OCFS2/Xen HA VM cluster, and i've 
got it working according to the instructions, but i'm very unhappy with 
the performance of the OCFS2 clustered filesystem (2 hours to copy a 10 GB 

VM image).

I'm starting to think that replacing OCFS2 with EVMS2 clustered containers 

might be the way to go, but i'd like to get some feedback by those who 
have done it before. Where is the best place to go to get some helpful 
discussion on this? If it makes any difference, the hardware is a Dell 
MD3000i iSCSI array, and two Dell 2950 servers, with HP ProCurve 
networking gear.

Paul

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