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authorEric Sandeen <sandeen@redhat.com>2008-05-26 12:29:46 -0400
committerTheodore Ts'o <tytso@mit.edu>2008-05-26 12:29:46 -0400
commit571640cad3fda6475da45d91cf86076f1f86bd9b (patch)
treea97ff3da9b60251c68358cd000c217cb37915ea2 /Documentation
parent034772b068be62a79470d6c1b81b01fbe27793ac (diff)
ext4: enable barriers by default
I can't think of any valid reason for ext4 to not use barriers when they are available; I believe this is necessary for filesystem integrity in the face of a volatile write cache on storage. An administrator who trusts that the cache is sufficiently battery- backed (and power supplies are sufficiently redundant, etc...) can always turn it back off again. SuSE has carried such a patch for ext3 for quite some time now. Also document the mount option while we're at it. Signed-off-by: Eric Sandeen <sandeen@redhat.com> Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/ext4.txt12
1 files changed, 10 insertions, 2 deletions
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 560f88dc709..0c5086db835 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -139,8 +139,16 @@ commit=nrsec (*) Ext4 can be told to sync all its data and metadata
Setting it to very large values will improve
performance.
-barrier=1 This enables/disables barriers. barrier=0 disables
- it, barrier=1 enables it.
+barrier=<0|1(*)> This enables/disables the use of write barriers in
+ the jbd code. barrier=0 disables, barrier=1 enables.
+ This also requires an IO stack which can support
+ barriers, and if jbd gets an error on a barrier
+ write, it will disable again with a warning.
+ Write barriers enforce proper on-disk ordering
+ of journal commits, making volatile disk write caches
+ safe to use, at some performance penalty. If
+ your disks are battery-backed in one way or another,
+ disabling barriers may safely improve performance.
orlov (*) This enables the new Orlov block allocator. It is
enabled by default.