"Glenn Dekhayser" gdekhayser@voyantinc.com writes:
Netapp recommends that you keep the fileysystems at 80% or less. Otherwise, WAFL starts to work very hard finding places to put data, and you'll see CPU spikes, High disk utilization, and degraded performance.
while Jeff Burton jburto1@yahoo.com writes:
We have a FAS940C that has 2 trad volumes (5TB & 3TB, 144GB/FC drives) that are always around 95%+ full because of funding and timing issues. Only when we run out of space do we start deleting snapshots, otherwise there are always a few hundred GB of snapshots. We've been running over 90% for the past year and have never had an outage or major hiccup...just a few disk failures. We typically have 4k-5k active CIFS connections and around 100 NFS connections. Clients have never noticed a performance problem, and our CPU utilization hovers between 30% and 50%. So maybe we do not notice a problem because there is more than enough CPU cycles left over for DOT/WAFL to deal with the full file system.
which seems a clear case of YMMV !
It's worth remembering that ONTAP already imposes a 10% reserve on the filing system size (including snapshot reserve); or on the sum of sizes, for flexible volumes in an aggregate. A "100% full" tradvol/aggregate is actually only using 90% of the blocks on the discs. Or looked at another way, the difference in congestion between "90% full" and "100% full" is 2:1, not infinity:1.
"Blake Golliher" thelastman@gmail.com writes:
A filer can be written to over 100% space utilization, it'll just keep growing. I've seen filers go up tot 107% space utilization before.
and "George, Andrew" georgea@anz.com replies:
Interesting We run a fair few filers in the 97%-99% arena, mainly as CIFS NAS devices. Every time I've seen it hit 100% 0 bytes available CIFS has refused to save anything.
That's my experience, with NFS. I would be interested (from a theoretical point of view!) to know how Blake gets the space utilisation that high. (Snapshot usage vs reserve as shown by "df" can go over 100%, of course.)