----- "Gary Bowers" <gbowers AT ITRUS DOT COM> wrote:

> My experience with direct connected iSCSI storage on a TSM server is
> that it gets abysmal performance unless you turn off Direct IO in
> TSM.  See other posts for that.  It is technically possible, but with
> the iSCSI limitation you might not want to use RMD "Raw Device
> Mapping" in VMware.  I am not sure on this, but it makes sense given
> what I have seen and read about here.  By the way, NFS and CIFS were
> equally bad performers for disk pools with DirectIO turned on.  They
> seem to really need the filesystem caching.  I'm "guessing" that
> putting the disks in a VMFS would help buffer the writes, and give
> you
> decent performance.
>
> It is something that would need to be tested first.  I'm confident
> that it would be much faster than WAN connection back to the States.
> Yuck.
>
> Good luck,
>
> Gary Bowers
> Itrus Technologies
>
> On Mar 11, 2010, at 1:18 PM, Ochs, Duane wrote:
>
> > Good day everyone,
> > Has anyone explored using TSM server (windows) on a VM using Iscsi
> > storage ? No library requirement at this time.
> > I have multiple European sites within close proximity of each other
> > and they have outgrown the WAN coming back to the states.
> > Only storage available there is Iscsi and they have a substantial
> > VMware implementation which would allow us to ride on a VM if
> > feasible/functional.
> >
> > Thoughts ?
> >
> > Thanks,
> > Duane


You probably would want the iSCSI storage linked back via VMWare and .vmdk 
image files so that Windows has no idea about it being iSCSI or otherwise - 
just a disk.  Gives you more flexibility in the long run, but you would want to 
test both Direct IO and not to see which performs best in your configuration.  
I would have thought leaving DIO on would be the best if there's another OS 
doing filesystem cache somewhere else, but could be wrong there ;)