We have a netapp storage environment where the majority of our resources exist for DR and have very little performance requirements meaning that we want to use large 1TB or 2TB 7200rpm SATA disks in most cases. We do have some production instances that need to exist on the same filer though where the 7200rpm SATA drives will not be sufficiently fast. Where we need multiple shelves of SATA disk for our DR we probably only need 1 or max 2 x 14 disk shelves or 1 x DS4243 with 15k SAS disks for these requirements.
I've been looking at the costs for the faster disks that we need and it actually would cost us only slightly more to get 2 x PAMII cards and stick with only SATA disks. In theory this would mean we'd get 15k SAS like performance with the benefits of the extra storage that larger SATA disks provides.
Does anyone have any feedback on this idea or any experiences with SATA performance increases using PAMII? Any feedback would be greatly appreciated!
It will depend on the workload. PAM helps reads but doesn't do much for writes. It will also help if your read load is not totally random and data is re-read.
If you have an existing NetApp storage environment on a PAMII-capable system running 7.3.2 or higher you can turn on the predictive cache statistics and you will be able to see what you would get if you had PAMII in the system. It will tell you how many disk reads would have been served by PAM.