On 03/02/2021 21:54, jos...@mailmag.net wrote: > Good Evening. > > I have a large BTRFS array, (14 Drives, ~100 TB RAW) which has been having > problems mounting on boot without timing out. This causes the system to drop > to emergency mode. I am then able to mount the array in emergency mode and > all data appears fine, but upon reboot it fails again. > > I actually first had this problem around a year ago, and initially put > considerable effort into extending the timeout in systemd, as I believed that > to be the problem. However, all the methods I attempted did not work properly > or caused the system to continue booting before the array was mounted, > causing all sorts of issues. Eventually, I was able to almost completely > resolve it by defragmenting the extent tree and subvolume tree for each > subvolume. (btrfs fi defrag /mountpoint/subvolume/) This seemed to reduce the > time required to mount, and made it mount on boot the majority of the time. >
Not what you asked, but adding "x-systemd.mount-timeout=180s" to the mount options in /etc/fstab works reliably for me to extend the timeout. Of course, my largest filesystem is only 20TB, across only two devices (two lvm-over-LUKS, each on separate physical drives) but it has very heavy use of snapshot creation and deletion. I also run with commit=15 as power is not too reliable here and losing power is the most frequent cause of a reboot.
