Hi,
tedapt <> [20080310 13:49:07 -0000]:
>
> [snipped lots of SD bits'n'bobs]
>
> I've found this rather alarming article on wikipedia which addresses
> the instability of the ext3 filesystem, specifically the section
> titled "No checksumming in journal" and the equally frightening
> footnotes 13 and 14 which are noted in it:
> http://en.wikipedia.org/wiki/Ext3#No_checksumming_in_journal. Tech.
> Systems tells me that they don't do "out-of-order" write caching,
> though I still wonder if this is related to the async vs. sync options
> in the mount options.
>
'sync' might overly write data to your filesystem[1] and just slow things
down un-necessarily. I would suggest if you want the 'effect' of sync
without the belts'n'braces you either:
1) play with /proc/sys/... to tweak (they exist for XFS[2]) how often the OS
writes dirty data to the filesystem
2) have a daemon that calls 'sync' every five or so seconds on an 'async'
mounted filesystem
3) call fsync after every filesystem write, making your system transactional
(but potentially dogslow)
> One response (from Andrew Taylor) to my original posting suggests
> creating large files in advance for all my writes, to avoid block
> allocation. Would others agree that would reduce the risk? If so, I
> could create a pool of files to write to once, then use them for my
> various writing needs.
>
Sounds like a good idea. Mentioned on the syslog-ng mailing list, syslog-ng
is getting circular logfile support (or already has?), this you might find
useful too.
I personally am surprised no one has suggested JFS, or am I missing
something? Support is already in the TS supplied kernel and memory/cpu wise
it is meant to be far more friendly[3] to hardware than XFS/ReiserFS/ext[23],
etc. This is what I am using on my SD cards, although I have only just
started recently to use it.
Cheers
Alex
[1] forget that it is an SD card for a moment, it's not relevant as correctly
pointed out they have wearleveling hardware hidden inside
[2] from the 2.6.25-rc4 changelog it *looks* like XFS is stable now on ARM,
you will have to backport the patch yourself though
[3] http://linuxgazette.net/102/piszcz.html
and http://www.debian-administration.org/articles/388
--
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