Hello, using Ubuntu server 18.04.2 btrfs on / 10 absolutely identical servers (Dell M630), with the same configuration, updated 2/10 and encountered this problem on both. After upgrading kernel from version 4.15.0-36-generic # 39-Ubuntu SMP observing at the same software configuration an increased load on the disk (write) - MySQL previously loaded the disk at 20-50 mB/s, after the update it started loading at 150-250 mB/s. MySQL configuration and package version were not changed. If I boot into the old kernel version (4.15.0-36), the problem disappears. Also tested kernels: 4.15.0-52 - problem persists 4.18.0-25 (hwe) - problem persists, load became more 200-250 mB/s 5.2-rc7 (vanilla) - problem persists Changing /var/lib/mysql partition to ext4 fixes the problem. With the help of Kai-Heng Feng in bugs.launchpad.net founded that this commit causes the regression: commit 31d11b83b96faaee4bb514d375a09489117c3e8d Author: Filipe Manana < fdmanana@xxxxxxxx > Date: Wed May 9 16:01:46 2018 +0100 Btrfs: fix duplicate extents after fsync of file with prealloc extents All the details you can find in the bug/1835185 at bugs.launchpad.net -- Igor Naumov
