On Mon, 31 Oct 2011, Cotton, Randall wrote:
Just to clarify: for me, raid group size = aggregate size - that is, I'll only have one raid group per aggregate.
I'm curious about this statement. Any reason why? What exactly is it that you are trying to accomplish?
I may not have answers to rg size vs. performance, but I can tell you that if you limit the sizes of your aggregates, performance *will* suffer in almost every case.
speaking) vs disk count. Anything (the more the merrier) that I can find which tests some kind of performance measure while varying only aggregate data disk count in the single and/or low double-digits would be helpful.
While you'll start seeing benefits of striping almost immediately, you won't get real gains for a full data center until you have many, many disks sharing the I/O load.
This doesn't seem to me an unreasonable thing to expect might be available somewhere. And it seems to me it's my professional responsibility to at least try to seek it out before recommending how we should (re)configure our boxes rather than being content to take a stab in the dark 8-)
The thing is, it's in the vendor's best interests to help you configure the units in a way that they perform well and meet your needs. Granted the vendor also wants to sell more hardware and more disks, but it's worth working with them and getting white papers about it.
The usual suggestions from NetApp were to use 16 disk RAID-DP raid groups and make the aggregates as big as possible -- that spreads the load, increases IOPS, and allows the array to move data around to avoid hot spots as it sees fit. Why make more work for yourself?
-Adam