Definitely want to spread across multiple shelves if possible. Not only does this give you better performance as the workload is distributed across the shelves, but it does actually give you better protection in the event of a shelf loss. We had a shelf failure on a system that had 10 aggregates distributed across 12 shelves. The system panic'd and rebooted and performance was horrible as it saw several aggregates with double drive failures and tried to rebuild them (ran out of online spares in the process) but we lost no data at all. NetApp's support was great about getting additional spare drives and a replacement shelf quickly. It took a couple of days for performance to return to 100% as it continued rebuilding the aggregates, but we lost no data and kept the system online during the rebuild after replacing the shelf.
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-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Ray Van Dolson Sent: Thursday, April 07, 2011 3:58 PM To: toasters@mathworks.com Subject: Distribute aggregate across shelves or limit to one shelf?
Best practice (based on my reading of the archives) seems to be to distribute disk membership in an aggregate across disk shelves.
This would appear to be for performance reasons primarily (less chance of saturating a shelf's "uplink" to the controller), but how does it affect reliability?
If I limit myself to one aggregate per shelf, if I lose that shelf I lose only the one aggregate. If aggregates are distributed I could lose all of them.
My thought is that the chance of the shelf failing is actually pretty slim as its hardware isn't all that sophisticated.
And obviously there are performance penalties for limiting to one aggregate per shelf (disk count maximums).
Thanks, Ray