I see this in my dmesg log
EXT4-fs (md1): re-mounted. Opts: commit=0 EXT4-fs (md2): re-mounted. Opts: commit=0 EXT4-fs (md3): re-mounted. Opts: commit=0 I think that means that dealloc is disabled? does mdadm not support dealloc?
- 1It appears that for some reason when a system is using ext4 on a RAID set, it wants to remount the set with the "commit=0" option set. I am currently seeing the same thing happen with 3ware hardware RAID. Like the original poster, I have no idea why this is happening. I am running two different OS's on the same hardware. Mandriva 2010.2 is NOT remounting with the commit option set, Mageia 1 is.user7836– user78362011-05-27 14:03:19 +00:00Commented May 27, 2011 at 14:03
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2 Answers
mdadm supports dealloc.
commit=sec is the time, the filesystem syncs its data and metadata. Setting this to 0 has the same effect as using the default value 5.
So I don't get the link between mdadm and commit=0 in your question?
- I guess I'm not sure why the system is remounting my FS's like this... I'm certainly not setting it to anything, and before I moved to mdadm raid I never saw this. 5 is something like what ext3 uses where I think the default for ext4 is something like 600xenoterracide– xenoterracide2010-09-01 22:49:21 +00:00Commented Sep 1, 2010 at 22:49
- 2I asked this question the LKML and the answer I got was that something though KDE/Hal was remounting the drives for some reason.xenoterracide– xenoterracide2010-10-30 12:42:27 +00:00Commented Oct 30, 2010 at 12:42
- 2To xenoterracide: Default 600 sec.? Here Kernel.org/doc/Documentation/filesystems/ext4.txt is something different: "... The default value is 5 seconds. ... Setting it to 0 will have the same effect as leaving it at the default (5 seconds). ..."user7578– user75782011-05-18 15:19:30 +00:00Commented May 18, 2011 at 15:19
RTFM mount(8)
commit=nrsec Sync all data and metadata every nrsec seconds. The default value is 5 seconds. Zero means default.
Very short.
New drives unload heads. Would then need base on commit size and run the risk of loosing 10 min of work to save wear and tear on disc.
