Jeff,
1) Mixing the stack types will actually work, but it's not supported due to performance issues. I have a setup like this in my environment, with two 3g and one 6g shelf on a 3g stack. It works okay, questionable throughput at times though.
Having a 6g stack on its own ports on a 3g card should not be an issue. I just put the very same online this week...
2) I don't believe you can get the 15k 3.5" drives from any vendor starting this year. The industry went en masse to the 2.5" form factor for various reasons. The smaller form factor is supposed to make up for the slower spindle speed w/r/t random read latency.
Fred
________________________________ From: Jeff Cleverley jeff.cleverley@avagotech.com To: toasters@teaparty.net Sent: Wednesday, February 27, 2013 8:33 PM Subject: DS2246 shelves and drives questions.
Greetings,
We will be upgrading an existing 6080 cluster to a 6280 cluster. We also have a 6080 cluster we'll be adding disks to also. Both clusters are 7-mode. We'll probably end up at 8.1 on both clusters. My 2 questions stem from the disks and shelves being proposed for the upgrades (ds2246 with 450g SAS).
1. We currently have DS4243 shelves with 600gig SAS. I know I can't mix these in the same stack because of the 3/6gb connection differences. I have a free port on each SAS adapter in our 6080s. Can I put the 6gb shelves on the same adapter as long as they are on their own stack? I'm guessing it may not be a best practice, but we don't have any slots free in the 6080 for more cards.
2. I found a white paper that states the 10K drive performance can be up to 20% slower than the 15K SAS drives for random reads. That seems like a pretty big performance it. It also says mixing the disks in aggregates is not recommended. Other than the smaller footprint and better density, I'm not seeing an advantage over using 600g SAS in the DS4243 shelves. Are there any advantages other than the faster SAS backend to warrant going to these shelves in our environment?
Thanks,
Jeff