May 27, 2009
So, you would think that 12 spindles would be...you know...fast.
Even if you took 12 spindles, made them into a RAID 10 array, they'd still be fast.
That's what I'd think, anyway. It turns out, my new EMC AX4 is having a bit of a problem. None of the machines hooked to it can reach > 30MB/s (which is 240Mb/s in bandwidth-talk). I haven't been able to determine the bottleneck yet, either.
I've discounted the switch. The equipment is nearly identical to that in the existing primary site (using SATA in the backup rather than SAS, but still, 30MB?). It isn't the cables. Port speeds read correctly (4GB from the storage array, 2GB from the servers).
The main difference is that the storage unit only has one processor, but I can't bring myself to believe that one processor can't push/pull over 30MB/s. I originally had it arranged as RAID 6, and I thought that maybe the two checksum computations were too much for it, but now with RAID 10, I'm seeing the same speed, so I don't think the processor is the bottleneck.
I'm just plain confused. This morning I'm going to be calling EMC. I've got a case open with their tech support, so hopefully I'll be able to get to the bottom of it. If it's something general, I'll make sure to write about it. If it's the lack of a 2nd storage processor, I'll make sure to complain about it. Either way, fun.