We are currently using HP MSA1500cs and looking to migrate to NetApp, probably FAS2020 or 2040. I'm trying to get an idea about performance.
Currently we have three servers attached to the MSA: Groupware server (Lotus Domino with 600 users), MS SQL server (serving Dynamics AX with 50 users) and a file server. We are looking to add two Citrix Xenserver hosts (using shared storage on the SAN) in the next 6 months or so.
Our current disk configuration on the MSA is:
Array A: 4x15k SCSI disks RAID10 for the Domino server data
Array B: 12x10k SCSI disks RAID5 for the SQL server and some of the file server data
Array C: 6x1TB SATA disks RAID5 for most of the file server data, Domino user e-mail archives and SQL server dumps.
Currently we don't seem to have any performance problems with this config.
NetApp representatives told me that performance wise, a FAS2020 with 12x1TB SATA disks is fast enough for us. I know it is terribly hard to quantify such things for sure, but I made some (possibly ridiculous) calculations based on ballpark figures available here: http://www.yellow-bricks.com/2009/12/23/iops/
Based on that I calculate that my existing config has:
Array A: 700 iops read or 350 iops write
Array B: 1500 iops read, 375 iops write
Array C: 450 iops read, 225 iops write
Total: 2650 iops read, 950 iops write
Using the same calculation, a RAID-DP of 12x7.2k rpm disks gives 900 iops read, 450 iops write. The question now is, does a NetApp with it's magical WAFL and all the other goodies really make up this lack of raw IOPS? What do people with real-life NetApp experience have to say?
Yes this seems very optimistic at best - you wont have a group of 12 drives in RAID-DP anyhow, because you will lose drives to spares and to the second controller. So maybe 1 group of 8 drives in DP, plus a spare, and one RAID 4 group plus a spare for the other controller. With the 2020 you really need more spindles to do anything much with SATA, or to use SAS drives IMHO.
Theoretically 12 SATA disks are not enough to cope with your workload, but if your NetApp representative is saying that because he analyzed performance data from your environment maybe he could be right, your current storage may be overprovisioned in term of IOPS.
Explain your IOPS consideration (which is mostly correct from a pure performance standpoint) to your NetApp representative and ask him why he said that.