pool import is slow due to many ZVOLs/snapshots
so updating from 9.10.1-U4 to 9.10.2-INTERNAL2, presents you with following.
Machine in question,
mode of update: FreeNAS webui updater using update-int.ixsystems.com
IMPI: 10.212.3.8 (admin/ADMIN)
steps to reproduce:
rollback https://stable-shark.ixsystems.com/ to U4 release, apply update to FreeNAS using webui updater using update-int.ixsystems.com. you should keep IMPI session handy, IMPI: 10.212.3.8 (admin/ADMIN)
1. takes a while to import a single pool > 3-4 min
#3 Updated by William Grzybowski about 3 years ago
- Status changed from Screened to Unscreened
- Assignee changed from William Grzybowski to Alexander Motin
mav, I am unsure what to do with this ticket. Regardless this seem out of depth for me since from his description, this is a pure ZFS thing.
Feel free to close if you don't think it is worth investigating.
#4 Updated by Alexander Motin about 3 years ago
- Status changed from Unscreened to Screened
I don't think this problem is related to the new version update. I've reverted to previous boot environment of 9.10.1-U4 and got the same pool import time of several minutes. I haven't proven yet what is the import delay cause, but I found huge delays of `zpool list
t snapshot`, caused by their number - there are 86762 snapshots on that pool, and attempt to list them first time causes huge delays due to disk seek time bottleneck.
#5 Updated by Alexander Motin about 3 years ago
- Status changed from Screened to Closed: Behaves correctly
Most of time spent during the pool import is spent on creation of devfs entries for 3300 zvol snapshots. Creation of each one require respective zvol properties to be read, performance of which is trivially limited by seek time of the disks. I don't think we can do much about this, rather then tell to not create so many snapshots (every 5 minutes for 2 weeks), especially for zvols.
#6 Updated by Alexander Motin almost 3 years ago
- Subject changed from pool import during boot process is slow to pool import is slow due to many ZVOLs/snapshots
- Status changed from Closed: Behaves correctly to Fix In Progress
I've found a way to improve pool import time in case of many ZVOLs/snapshots by several times (from 40 to 10 seconds on my test setup with 1 ZVOL and 1000 snapshots).