We currently have a FAS270c. It will be running ONTAP v188.8.131.52. by the time we add new disks. Our current RAID DP group is 15 disks, with 1 global spare. We just purchased 4 more disks. In my research I found that I could increase the raidgroup as large as 28. So my question is this:
Is there any downsides/snafu's to running our aggregate on a single raidgroup of 19 ( or 28 for that matter ) disks?
We do not run databases or Exchange on this filer, its solely for CIFS shares.
No inherent issue with taking an FC RAID group up to 20 disks -- basically with larger RAID groups it's a trade-off between space utilization (better if larger RG's) and rebuild times (longer if larger RG's).
I'm generally quite comfortable with FC RAID groups up to 20 disks as the rebuild time is still pretty good. What I might even recommend is just adding 3 disks and going up to (2) hot spares as that will enable Maintenance Center -- see tip #2 here for details on what that is.
If they're not too technical/there's more important things to discuss, I'll just recommend 1 hot spare if only 1 shelf or just 2020/2040 internal disks (i.e. 12 or 14 disks). Once there's a 2nd shelf added, I'll usually recommend 2 hot spares noting that they can always add the 2nd hot spare later.
But.....if they are more technical and/or there's benefit in helping them understand all the "NetApp-y goodness under the covers" I'll wander into Maintenance Center a bit.
Side-note: I personally really try to stay away from internal-disk-only 20x0 HA configurations.....the usable space calcs just end up getting really painful to explain/justify. Unless the customer has a specific need for HA, I'll often go more towards a single head with 4 Hour support. Sharing hot spares between heads (dynamic software disk ownership would seem to be the most likely way to do it) would be one way to help there a bit.