We just installed two 1TB SATA shelves (28 spindles) that I want to configure in a single aggregate. These are the only 1TB shelves in the environment, so I need to dedicate two spindles (preferably one per shelf) as hot spares. I'm trying to figure out what raid config will give me the least amount of stranded drives yet maximize my usable space since the max aggregate size in DOT 7.3.2 is 16TB (19 data disks). Here's what I've come up with so far but I also need to take into account performance.
1) 5 RGs of 3D+2P = 25 used, 1 leftover. This gives me roughly 10TB usable space so I'm missing out on almost 6TB.
2) 4 RGs of 4D+2P = 24 used, 2 leftover. Only gets me one extra data disk.
3) 3 RGs of 5D+2P = 21 used, 5 leftover. But I could add another RG of 3D+2P. How does the third smaller RG effect performance? Essentially maximizes my usable space and strands 0 spindles. Thinking this is the best option assuming the mismatched RGs do not hinder performance.
4) 3 RGs of 6D+2P = 24 used, 2 leftover. essentially maximizes usable space.
5) 2 RGs of 9D+2P = 22 used, 4 leftover, essentially maximizes usable space.
Any recommendations? Am I on the right track here in my thinking that no matter what the RG size, if I can get 19 data disks I will be maximizing my usable space?
Thanks for the insight,
Jeff
