Barriers and journaling filesystems [LWN.net]

Barriers and journaling filesystems

Posted May 21, 2008 19:50 UTC (Wed) by jengelh (subscriber, #33263)
Parent article: Barriers and journaling filesystems

XFS has barriers enabled by default since 2.6.17, and it still seems to perform well (on the
last server where I put it on without disabling barriers).

^1 http://lkml.org/lkml/2006/5/22/278

(Log in to post comments)

XFS / LVM

Posted May 21, 2008 20:29 UTC (Wed) by tarvin (subscriber, #4412) [Link]

Do XFS' barriers work if the file system is created on an LVM2 logical volume?

XFS / LVM

Posted May 21, 2008 20:47 UTC (Wed) by nix (subscriber, #2304) [Link]

device-mapper doesn't pass the barriers down, so no. (Actually it asserts 
that it doesn't support barriers, which is safer: the fs can take that 
into account rather than firing off barriers which are just ignored).

(Maybe this has changed recently, but this was the state of affairs a 
month or so back.)

XFS / LVM

Posted May 21, 2008 21:10 UTC (Wed) by jengelh (subscriber, #33263) [Link]

Correct.

[ 51.404922] Filesystem "dm-0": Disabling barriers, not supported by the underlying device [27138.731115] Filesystem "dm-1": Disabling barriers, not supported by the underlying device

Even though I know from before my time of using dm-crypt that only one of sda or sdb does not support barriers at the hardware level.

Barriers and journaling filesystems

Posted May 22, 2008 20:29 UTC (Thu) by mikachu (guest, #5333) [Link]

Disabling barriers on xfs increases performance very very much in some situations, especially
when deleting a directory tree with many small files, eg the linux-2.6 tree. With barriers it
takes something like 2-3 minutes and without barriers around 20 seconds. (These numbers are
from my memory).