"Glenn Dekhayser" gdekhayser@voyantinc.com writes:
Actually, the aggregate snap reserve is by default only 5%, not 10%.
... which is nothing to do with the 10% "reserve" I was talking about, which is at a lower level. See below.
"Max" slinkywizard@integraonline.com adds:
Somewhat tangental:
Does anyone here use aggregate snap reserves ? I was under the impression that is was only useful for sync mirror setups... So I usually just shut it off to take advantage of the extra space.
Whatever NetApp say, I've never seen the point of reserving space for aggregate snapshots if you don't _use_ aggregate snapshots for anything. We don't, so
snap reserve -A [aggrname] 0 snap sched -A [aggrname] 0
However, for pedagogic purposes, I've set it back to 5% temporarily for the example below. :-)
carina> df -A main Aggregate kbytes used avail capacity main 595174120 575814948 19359172 97% main/.snapshot 31324952 0 31324952 0%
That's a total of 626499072 KB, _including_ the snapshot reserve.
carina> aggr status main -r Aggregate main (online, raid_dp) (block checksums) Plex /main/plex0 (online, normal, active) RAID group /main/plex0/rg0 (normal)
RAID Disk Device HA SHELF BAY CHAN Pool Type RPM Used (MB/blks) Phys (MB/blks) --------- ------ ------------- ---- ---- ---- ----- -------------- -------------- dparity 8b.24 8b 1 8 FC:A - FCAL 10000 68000/139264000 68552/140395088 parity 8a.27 8a 1 11 FC:B - FCAL 10000 68000/139264000 68552/140395088 data 8b.28 8b 1 12 FC:A - FCAL 10000 68000/139264000 68552/140395088 data 8a.29 8a 1 13 FC:B - FCAL 10000 68000/139264000 68552/140395088 data 8a.25 8a 1 9 FC:B - FCAL 10000 68000/139264000 68552/140395088 data 8b.22 8b 1 6 FC:A - FCAL 10000 68000/139264000 68552/140395088 data 8b.16 8b 1 0 FC:A - FCAL 10000 68000/139264000 68552/140395088 data 8a.17 8a 1 1 FC:B - FCAL 10000 68000/139264000 68552/140395088 data 8b.18 8b 1 2 FC:A - FCAL 10000 68000/139264000 68552/140395088 data 8a.19 8a 1 3 FC:B - FCAL 10000 68000/139264000 68552/140395088 data 8a.21 8a 1 5 FC:B - FCAL 10000 68000/139264000 68552/140395088 data 8a.23 8a 1 7 FC:B - FCAL 10000 68000/139264000 68552/140395088
After the right sizing of the discs to 68000 MB = 69632000 KB, taking off 20.5 MB = 20992 KB (the reserved area at the start of each disc: it's been that ever since NetApp was hatched from the cosmic egg) that's a total of 10 (data discs) x 69611008 KB (per disc) = 696110080 KB.
The space actually made available in the aggregate to flexible volumes, their snapshots, and aggregate snapshots, old Uncle Tom Cobley and all, is 90% of that, i.e. 696110080 * 0.9 = 626499072 KB.
[It would have made a better lesson if 90% of 10 data discs hadn't equalled exactly 9 data discs! Sorry about that, you'll just have to count them carefully ...]
Exactly the same (hidden) reserve applies in a traditional volume.
[Oh, and to you guys over in the "Aggregate size question" thread, stop quoting all your figures in GB and to 2+ sig figs, as it's imposible to make anything add up if you do that. Real Programmers aren't scared of 10-figure numbers :-) ]