2011-10-05 10:20 AM
In the storage management guide there is this (page 158):
The root aggregate contains the root volume. Starting with Data ONTAP 8.1, new systems are
shipped with the root volume in a 64-bit root aggregate. The root aggregate should contain only the
root volume. You must not include or create data volumes in the root aggregate.
Then there is this (page 159):
Alternatively, the root volume can exist as a FlexVol volume that is part of a larger hosting
What is this saying? Is this a change in 8.1 or the same old "best practice" to segregate the root volume on a root aggregate unless you are disk-constrained and need the space? Would not the "larger hosting aggregate" be the root aggregate which the previous statement says we "must not include or create data volumes in the root aggregate?"
2011-10-05 10:37 AM
We have had similar debates on this forum and you can find the debate on both sides. We tend to setup separate root aggregates (3 drive) for larger systems and for smaller systems it is not feasible. The issue is an edge case...a corner case that is rare where if there is corruption of an aggregate and it needs to be repaired with wafliron/waflcheck then a smaller 3 drive root can be rebuilt quickly to keep the controller running while it hot repairs other aggregates...the more volumes in an aggr the more to go through and wait to bring online.
Another way to have redundancy...if a system has 2 aggrs...then you can snapmirror the root volume to the other aggregate...if the root aggr has an issue you can then mark a new AUTOROOT then break the mirror and mark it as root and reboot again to recover root that way... works well and a few steps to not have a separate 3 drive root and also have redundancy. I take this on a case by case basis on professional services... often a large system we have 3 drives to spare for a separate root... on a 2040 or 3210 we often don't. In any event, the odds of any issue are rare but we like to plan for all possible issues.
2011-10-05 10:54 AM
I've read some of the other debates around this but the first paragraph I quoted isn't in the 8.0x documentation and I was wondering if this was a new "requirement" in the 8.1 release or just CYA language.
2011-10-05 10:58 AM
The update is that the root volume on a new system is 64bit where in 8.0 it was 32bit. So the docs were udpated to show the new aggr type for root. As well as having 0% aggr snap reserve and 5% vol reserve. The best practice is still a depends answer which sparks the debate. We have debate about it internally with our SEs as well.. I would love to see ONTAP installed on SSDs internal or something portable or migrate capable in a head swap and not take 3 drives in a shelf.