On Jan 2, 2013, at 8:45 PM, Geoff Nordli <geo...@gnaa.net> wrote:

> I am looking at the performance numbers for the Oracle VDI admin guide.
> http://docs.oracle.com/html/E26214_02/performance-storage.html
> From my calculations for 200 desktops running Windows 7 knowledge user (15 
> iops) with a 30-70 read/write split it comes to 5100 iops. Using 7200 rpm 
> disks the requirement will be 68 disks.
> This doesn't seem right, because if you are using clones with caching, you 
> should be able to easily satisfy your reads from ARC and L2ARC.  As well, 
> Oracle VDI by default caches writes; therefore the writes will be coalesced 
> and there will be no ZIL activity.

All of these IOPS <--> VDI users guidelines are wrong. The problem is that the 
variability of
response time is too great for a HDD. The only hope we have of getting the 
calculations to work is to reduce the variability by using a device that is 
more consistent in its
response (eg SSDs).

> Anyone have other guidelines on what they are seeing for iops with vdi?

The successful VDI implementations I've seen have relatively small space 
requirements for
the performance-critical work. So there are a bunch  of companies offering 
SSD-based arrays
for that market. If you're stuck with HDDs, then effective use of 
snapshots+clones with a few
GB of RAM and slog can support quite a few desktops.
 -- richard



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