[nflug] Virtualization

Sat Dec 20 21:30:38 EST 2008

We use Xen Enterprise (commercial Xensource Xen) for our DEV/QA environments.  We have 4 high end Dell's (dual Quad core 5365 Xeons iwht 600GB of disk and 32 GB of ram) running 18-23 VM's 1-2G Ram each.   By far we have found it to be a fantastic investment.  I personally setup the systems and handle day to day mgmt.   The only downer I personaly have with Xensource is the mgmt console is windows only (which i run on a virtualbox WinXP vm on my personal ubuntu workstation).  the main reason we went with commercial xen was that it is proven and we needed to be able to ru na few Windows VM and they needed to be maximal performers.

Ours VM's are FC4-6 (not supported by Xen but I found some creative solutions), Centos5.x, and Windows 2000 and XP.  all perform remarkably well.  We don't have a shared storage backend (SAN) for these, so we don't utilize live migration or Xen clusters, so I can't comment on hos that part works or not.

Things to remember, is that your Hosts will need to be sized to handle your guest IO loads,  and  in the case of Xen,  if one VM monopolizes IO bandwidth, the other VM's can suffer,  so size the disks and network BW appropriately (GB minimum).  The more RAM the better, and more CPU cores helps a lot (the dual quads in our case were a excellent choice).

It also helps to not stick all of your high demand VM's all on the same xenhost (i.e.  don't stick 8 busy oracle servers on it).  Virtual machiens have overhead,  and the most where I've seen the limits for xen is I/O (we have version 4.x,  version 5.x is supposedly much better in this regard).   Also cpu bound performance is as good as native as far as I can see it (within a couple percent).  I'm not sure about VMware's esx in this regard,  but the design of vmware (dynamic recompilation), vs' xen's paravirtualization tells me that xen wil be far ahead for cpu bound tasks, and vmware may take the lead slightly on IObound tasks (depends on the io, whether, disk based or network).

 -- David J. Andruczyk

________________________________
From: Brad Bartram <brad.bartram at gmail.com>
To: nflug at nflug.org
Sent: Monday, December 15, 2008 1:41:25 PM
Subject: [nflug] Virtualization

I'm interested in this whole virtualization of servers and services trend that's been on going for quite a while.  I've worked with it on workstations and in the traditional host - guest configurations to gain access to non-native applications - you know, user-level stuff.  I'm interested in it on the server side of things though.  I've read the marketing propaganda and seen the vendor white papers and all the trade news-vertisements, but I'm interested in hearing some real world opinions.

I know some of you have opinions on it.  So what's the good, the bad, the shortcomings, and the strengths?  Are there any things I should look out for or things I should consider in planning out hardware purchases and such?

Thanks

Brad

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