Do you mean that there is a performance issue with that particular VM, or with other systems on the filer that are caused by I/O on that VM?

You should be able to use flex share to set a lower priority for a "cache-hogging" and reduce its impact on the other volumes. On the command line, run "priority on." Then run "priority set volume $volumename level=Low" for the problem volume. This will give less priority to that volume in the write cache, free up the cache for other things, and (hopefully) reduce latency on those other volumes.

In your case, you'll need to have that RDM in its own volume.

    From: Alon Zeltser <alonz@emet.co.il>
 To: toasters@teaparty.net 
 Sent: Tuesday, December 6, 2011 6:00 AM
 Subject: limit i/o for lun or volume

Hi all
i have a situation of a virtual machine running on esx 4.0 over iscsi
this machine  (while the user is running his stuff)  is using a lot of 
i/o on a very small netapp controller (2020) with only 5 data disks aggr
and getting very bad latency and eventually getting a lun reset errors 
and the machine freeze for a few minutes
i have increased the timeouts from the windows side but it doesn't seems 
to help
this application don't need so much i/o and can be run a 5.4k disk on an 
old laptop but given the resources of netapp it uses them to the fullest
it is important to mention that this application is running over MSSQL 
db and the i/o problem goes to rdm lun
my question: is there a way to limit the i/o of this machine from either 
netapp side /vmware side / windows side / network side
i'm aweare of vmware storage i/o control but this is only supported in 
vsphere 4.1 and an upgrade is not an
 options right now
i'm also aware of flexshare from the netapp side but i don't think 
giving low priority to this volume will help in this case
is there other way you can think of to limit the i/o goes from vmware 
virtual machine through iscsi to an rdm lun or his hosting volume?

thank you

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