Howdy folks,
I recently moved the Minecraft server (a rather large world that’s been running continuously for 10 years now) from it’s spinning rust ZFS mirror to an NVME-backed ZFS mirror.
Quite alarmingly, the FRAG statistic has rapidly taken on a life of its own.
This is how it started two weeks ago…
NAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
pool 880G 102G 778G - - 0% 11% 1.00x ONLINE -
mirror-0 880G 102G 778G - - 0% 11.6% - ONLINE
nvme-WD_Red_SN700_1000GB_XXXXXXXXXXXX-part1 882G - - - - - - - ONLINE
nvme-WD_Red_SN700_1000GB_XXXXXXXXXXXX-part1 882G - - - - - - - ONLINE
After finishing copying over the data and running the server off of the new NVME mirror for a week…
NAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
pool 880G 197G 683G - - 9% 22% 1.00x ONLINE -
mirror-0 880G 197G 683G - - 9% 22.4% - ONLINE
nvme-WD_Red_SN700_1000GB_XXXXXXXXXXXX-part1 882G - - - - - - - ONLINE
nvme-WD_Red_SN700_1000GB_XXXXXXXXXXXX-part1 882G - - - - - - - ONLINE
then a few days later…
NAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
pool 880G 200G 680G - - 13% 22% 1.00x ONLINE -
mirror-0 880G 200G 680G - - 13% 22.7% - ONLINE
nvme-WD_Red_SN700_1000GB_XXXXXXXXXXXX-part1 882G - - - - - - - ONLINE
nvme-WD_Red_SN700_1000GB_XXXXXXXXXXXX-part1 882G - - - - - - - ONLINE
a few more days…
NAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
pool 880G 200G 680G - - 14% 22% 1.00x ONLINE -
mirror-0 880G 200G 680G - - 14% 22.7% - ONLINE
nvme-WD_Red_SN700_1000GB_XXXXXXXXXXXX-part1 882G - - - - - - - ONLINE
nvme-WD_Red_SN700_1000GB_XXXXXXXXXXXX-part1 882G - - - - - - - ONLINE
a few imore days later…
NAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
pool 880G 202G 678G - - 15% 22% 1.00x ONLINE -
mirror-0 880G 202G 678G - - 15% 23.0% - ONLINE
nvme-WD_Red_SN700_1000GB_XXXXXXXXXXXX-part1 882G - - - - - - - ONLINE
nvme-WD_Red_SN700_1000GB_XXXXXXXXXXXX-part1 882G - - - - - - - ONLINE
In a month it’ll be what, 100% fragmented?
Is this thing going to implode on me?
I realize ZFS fragmentation is “just” a measure of the availability of contiguous free block regions. As a COW-based filesystem this is going to happen but it’s not (as moderate levels) a big deal. I have read.
Questions:
When does fragmentation get to be a big deal?
What is to be done so that it doesn’t get to be a big deal?
Perhaps there is Minecraft ZFS tuning?
Thanks as always for your feedback and insights.