topic Re: Mystical Aggregate Performance in ONTAP Discussions

Mystical Aggregate Performance

joostvandrenth — Thu, 05 Jun 2025 07:08:42 GMT

I am looking at a filer with a lot of aggregates consisting of SATA. To make out what is what and reorganize some vols to higher performance aggregates I am trying to use the perf advisor to help me figure out which vols are using a lot of I/O.

I made some groupings of all the vols inside an aggregate and compared top objects -> vol IOPS to the IOPS generated by the underlying aggregate, suprise surprise: I have 3 aggregates consisting of 16 drives SATA each generating a consistent 1000-1200 IOPS with NO I/O showing for the volumes/LUNs inside each aggregate. No reallocates are running (also no measurements done), no snapmirrors on those aggrs. I cannot find out which process is generating those 1.000+ I/O per aggregate.

Re: Mystical Aggregate Performance

BrendonHiggins — Tue, 14 Sep 2010 14:01:30 GMT

NDMP backup or snapmirror / snapvault jobs running?

Can you see the IO via sysstats -x?

Bren

Re: Mystical Aggregate Performance

joostvandrenth — Tue, 14 Sep 2010 18:00:20 GMT

No Snapvault licenses, NDMP would actually be possible - will need to check on this. Sysstat -x shows me overall performance, with another 10 aggregates active on the system I see no way to isolate this to anything particular to my aggregate....

Re: Mystical Aggregate Performance

pascalduk — Wed, 15 Sep 2010 06:03:20 GMT

I have had this mystery in the past. In my case I had a lot of post snapshot house keeping jobs. You can view for a specific volume what is going on.

"priv set advanced; wafl scan status <volume name>"

On a completely idle volume you should only see a "active bitmap rearrangement" scan.

Snapshot related scans are:

snap create summary update

blocks used summary update

container block reclamation

And perhaps deduplication could be active.

Re: Mystical Aggregate Performance

joostvandrenth — Tue, 26 Oct 2010 21:21:23 GMT

spot on! much obliged!