Mailinglist Archive: opensuse (2086 mails)
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Re: [opensuse] reiser and ext3 confusion
- From: Jan Engelhardt <jengelh@xxxxxxxxxxxxxxx>
- Date: Fri, 17 Aug 2007 16:19:20 +0200 (CEST)
- Message-id: <Pine.LNX.4.64.0708171612340.30502@xxxxxxxxxxxxxxxxxxxxxxxxx>
On Aug 17 2007 15:53, Clayton wrote:
>What is the default for ext3 in SUSE? Journal, Ordered or Writeback?
I suppose whatever is ext3's default.
>What about defragmentation? As far as I know, ext3 cannot be properly
>defragmented either on the fly or off line. (Also none for Reiser,
>but I find that Resier tends to stay relatively neat and tidy... for
>the most part). Is file fragmentation on ext3 something a user needs
>to think about?
Almost no filesystem does defragmentation. In fact, they just allocate things
smart in the first place.
>Does ext still default to doing a filesystem scan on every 10th or
IIRC it does.
>If it does, what do you recommend for computers that are
>booted up and turned off on a regular basis (like laptops)?
Of the stable ones? jfs, xfs.
Of the ones in development? reiser4, btrfs ;-)
>I am helping a friend convert his laptop to openSUSE10.2 this
>weekend... so file system choice is on my mind. Upgrade from ext2 to
>ext3 to ext4 is not much of an issue so not a reason to choose ext3
>here - neither is scalability since it's just a laptop. I need
>something that will give little trouble with things like sudden
>unintentional powerdowns - something Reiser usually survives nicely
>with a journal replay on boot after an uncontrolled shutdown.
>What can happen with ext3 after an uncontrolled power off? Does it survive as
>cleanly as Reiser does (usually) or are you usually back to booting a rescue
>system and forcing an fsck to be able to remount the filesystem? (this is a
>situation I don't want for this new user if I can avoid it, and was my
>experience waaaay back when I used ext)
After an fs repair, I'd always reboot, unless you can really unmount the mount.
Which you cannot with your root vfsmount (it will just switch to readonly)
unless you use tricks that are reserved for the true linux gods. (Then again,
rebooting is faster than trying to play with pivot_root.)
The question is what happens to <any filesystem> after an uncontrolled power
off. reiser4 advertises atomicity "either it's there, or it's not", other
filesystems have something similar. Then things get worse, like a file whose
data pointer points nowhere because we were just writing it, etc. Ordered
journals can help this at the cost of speed at various levels.
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