On 10/24/2013 01:59 PM, John R Pierce wrote: > 1) 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. > 2) 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. > 3) 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?