On 2014-07-07 09:54, Konstantinos Skarlatos wrote: > On 7/7/2014 4:38 μμ, André-Sebastian Liebe wrote: >> Hello List, >> >> can anyone tell me how much time is acceptable and assumable for a >> multi-disk btrfs array with classical hard disk drives to mount? >> >> I'm having a bit of trouble with my current systemd setup, because it >> couldn't mount my btrfs raid anymore after adding the 5th drive. With >> the 4 drive setup it failed to mount once in a few times. Now it fails >> everytime because the default timeout of 1m 30s is reached and mount is >> aborted. >> My last 10 manual mounts took between 1m57s and 2m12s to finish. > I have the exact same problem, and have to manually mount my large > multi-disk btrfs filesystems, so I would be interested in a solution as > well. > >> >> My hardware setup contains a >> - Intel Core i7 4770 >> - Kernel 3.15.2-1-ARCH >> - 32GB RAM >> - dev 1-4 are 4TB Seagate ST4000DM000 (5900rpm) >> - dev 5 is a 4TB Wstern Digital WDC WD40EFRX (5400rpm) >> >> Thanks in advance >> >> André-Sebastian Liebe >> -------------------------------------------------------------------------------------------------- >> >> >> # btrfs fi sh >> Label: 'apc01_pool0' uuid: 066141c6-16ca-4a30-b55c-e606b90ad0fb >> Total devices 5 FS bytes used 14.21TiB >> devid 1 size 3.64TiB used 2.86TiB path /dev/sdd >> devid 2 size 3.64TiB used 2.86TiB path /dev/sdc >> devid 3 size 3.64TiB used 2.86TiB path /dev/sdf >> devid 4 size 3.64TiB used 2.86TiB path /dev/sde >> devid 5 size 3.64TiB used 2.88TiB path /dev/sdb >> >> Btrfs v3.14.2-dirty >> >> # btrfs fi df /data/pool0/ >> Data, single: total=14.28TiB, used=14.19TiB >> System, RAID1: total=8.00MiB, used=1.54MiB >> Metadata, RAID1: total=26.00GiB, used=20.20GiB >> unknown, single: total=512.00MiB, used=0.00
This is interesting, I actually did some profiling of the mount timings for a bunch of different configurations of 4 (identical other than hardware age) 1TB Seagate disks. One of the arrangements I tested was Data using single profile and Metadata/System using RAID1. Based on the results I got, and what you are reporting, the mount time doesn't scale linearly in proportion to the amount of storage space. You might want to try the RAID10 profile for Metadata, of the configurations I tested, the fastest used Single for Data and RAID10 for Metadata/System. Also, based on the System chunk usage, I'm guessing that you have a LOT of subvolumes/snapshots, and I do know that having very large (100+) numbers of either does slow down the mount command (I don't think that we cache subvolume information between mount invocations, so it has to re-parse the system chunks for each individual mount).
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