Red Hat Bugzilla – Bug 783514
Documentation for default barrier setting for EXT3 filesystems in mount manpage is wrong
Last modified: 2013-02-21 05:22:42 EST
Description of problem:
According to the man-page for the mount command EXT3 filesystems are mounted with barriers disabled by default, even tough on RHEL6 barriers are enabled by default for both EXT3 and EXT4 filesystems:
# man mount
Mount options for ext3
barrier=0 / barrier=1
... The ext3 filesystem does not enable write barriers by default.
This sentence should be changed to:
The ext3 filesystem enables write barriers by default.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. man mount
2. search for barrier option for EXT3
Here's what the default mount options for a EXT3 FS look on one of my RHEL6 systems:
# grep ext3 /proc/mounts
/dev/mapper/vg_cor_scs-lv_cor_scs /usr/sap/COR/SCS00 ext3 rw,relatime,errors=continue,barrier=1,data=ordered 0 0
The FS was monuted with the default options, there is no entry in /etc/fstab specifying that barriers should be enabled for this FS.
This request was evaluated by Red Hat Product Management for
inclusion in the current release of Red Hat Enterprise Linux.
Because the affected component is not scheduled to be updated
in the current release, Red Hat is unfortunately unable to
address this request at this time. Red Hat invites you to
ask your support representative to propose this request, if
appropriate and relevant, in the next release of Red Hat
Enterprise Linux. If you would like it considered as an
exception in the current release, please ask your support
mount(8) man page is part of the util-linux-ng package. Changing to the correct component.
# rpm -q util-linux-ng
# man 8 mount
barrier=0 / barrier=1
This enables/disables barriers. barrier=0 disables it, barrier=1 enables it.
Write barriers enforce proper on-disk ordering of journal commits, making volatile
disk write caches safe to use, at some performance penalty. The ext3 filesystem
enables write barriers by default. Be sure to enable barriers unless your disks
are battery-backed one way or another. Otherwise you risk filesystem corruption
in case of power failure.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.