Re: Far too long mount time
flat view
From: Andreas Dilger <hidden>
Date: 2012-08-16 09:09:55
On 2012-08-16, at 1:54 AM, Javier Marcet wrote:
I'm in the process of setting up a new software raid with four 3TB disks. So far I'm doing the tests using also bcache on a 60GB partition on a 120GB SSD. Everything is protected by a UPS. On the software side: self compiled kernel 3.5.1 and util-linux 2.20.1 Thus far, ext4 is doing really really well but for one thing, the mount time. At the moment I'm testing a RAID5 which makes the partition 8.2TB. ext4 takes: $ time mount /mnt/raid 0.00s user 79.49s system 92% cpu 1:26.25 total xfs, OTOH, is way faster: time mount /mnt/raid 0.00s user 0.01s system 0% cpu 1.869 total I'v tried everything I could think of but the mount time remains constant. Is there anything I can do to speed up the mount time?
Did you format the filesystem with "mke2fs -t ext4"? Without the "-t ext4" option, you won't get the "flex_bg" formatting option, which improves the layout of the filesystem metadata, and definitely reduces mount times. It is a bit strange that _mounting_ uses 92% CPU. Hmm, there was a bug reported for 3.5.1, see "Re: Upgraded from 3.4 to 3.5.1 kernel: machine does not boot", and reverting the patch with git commit hash "8aeb00ff85ad25453765dd339b408c0087db1527" resolved the problem. This slowdown was only seen with larger devices. Cheers, Andreas