On Mon, 31 Oct 2011, Cotton, Randall wrote:
No argument there. There are 3 separate geographical sites, though, and HA was desired everywhere. For what it's worth, I was brought on after the purchase.
Heh, ain't that always the way? It's trouble when you start inheriting someone else's problems. :)
Ooh, yes, quite correct. 16 disks per raid group, not aggregate, is what I meant. Thanks for correcting that.
No problem.
However, in an *aggregate*, the more spindles you have (that is, the more raid groups, since you want to add full raid groups when you can), the better the performance, and it does keep going up because the I/O spreads out more and more as you go to very wide stripes.
This is an important distinction and though I'm not able to afford the luxury yet of multiple aggregates per node, it's an excellent point to make and keep in mind.
Well, so given what you have, 6x(14+2)=96. It seems odd to not have purchased at least that many drives -- you can't even have one full 16 disk rg per filer head. Your best bet is probably just to take the drives you have, split them evenly among the heads, and create 16 disk raid groups from them (when you add drives later, fill in the rest of the data drives for the current rg first). Of course, again this is without knowing the various use cases for each of the locations.
The main thing is that rather than thinking "one raid group = one aggregate", you should be thinking "many raid groups make up a single aggregate". I would stick to 16 disk groups -- you can create partial groups for now, but as you grow try to make the purchases in rg sizes. Keep growing that aggregate over time when you make additional disk purchases until you've reached the maximum aggregate size, and then start another one. There are very few cases where you want a separate aggregate (syncmirror used to care -- not sure it does anymore).
I hope for your sake they are at least FC drives and not SATA.
-Adam