[OpenAFS] openafs fileservers in VMware ESX

Matthew Cocker matt@cs.auckland.ac.nz
Thu, 21 Apr 2005 16:28:57 +1200

The question is how much does the overhead of virtualisation (which with 
afs is not much) actually matter with an AFS fileserver and the client 
side caching.

The data I have collected over time on our hardware server suggests that 
our afs servers while containing a lot of data and user volumes are not 
very heavily loaded and 95% of the time we are underutilizing the 
hardware we had with it sitting at 1-2 % cpu, not using much memory, the 
GB network links idling and the disk IO requirements not the heavy on 

We also have had to deal with large budget cuts which meant we could not 
purchase what we have been able to in the past nor afford to run it.

ESX allows us to share HBA's, FC ports for multiple hosts meaning less 
FC overhead in setting it up. We are using 70% less power, need less 
cooling and less space.

We now have less (higher quality) servers than we did before so harware 
support cost has dropped. Also even with multiple AFS FS servers running 
on a single ESX box we do not see any IO issues yet. If we ever do we 
can just vmotion the problem server to another underulitlised ESX server 
(without having to shutdown the FS server in about 1 minute).

We also have a three year lease cycle that means we have to swap servers 
hardware on a regular basis, but with vmotion and shared sans luns we do 
not need to use vos move.

If we have any problem volumes/apps we have a couple of hardware afs 
servers for them. But so far apart from the issues with vos listvol 
(which works but is slow) we have not had any issues.

We are working into it slowly with only about 1Tb of 4Tb of data in VM 
afs servers and we can always back out if we run into big problems but 
we had not seem any issues in testing because we did scale it up enougn.



Derek Atkins wrote:
> I've never seen any reason to virtualize an AFS server.  Ever.  The key is IO
> bandwith, which isn't increased by virtualization.  You really want separate
> PHYSICAL servers for AFS servers.  Virtualization does not give you any
> benefits due to hardware failure, power failure, or any other failure.  It just
> adds overhead.
> -derek