On 10/24/2013 01:59 PM, John R Pierce wrote:
- you need a LOT of ram for decent performance on large zpools. 1GB ram
above your basic system/application requirements per terabyte of zpool is not unreasonable.
That seems quite reasonable to me. Our existing equipment has far more than enough RAM to make this a comfortable experience.
- don't go overboard with snapshots. a few 100 are probably OK, but
1000s (*) will really drag down the performance of operations that enumerate file systems.
Our intended use for snapshots is to enable consistent backup points, something we're simulating now with rsync and its hard-link option. We haven't figured out the best way to do this, but in our backup clusters we have rarely more than 100 save points at any one time.
- NEVER let a zpool fill up above about 70% full, or the performance
really goes downhill.
Thanks for the tip!
(*) ran into a guy who had 100s of zfs 'file systems' (mount points), per user home directories, and was doing nightly snapshots going back several years, and his zfs commands were taking a long long time to do anything, and he couldn't figure out why. I think he had over 10,000 filesystems * snapshots.
Wow. Couldn't he have the same results by putting all the home directories on a single ZFS partition?