[TUHS] The evolution of Unix facilities and architecture

Michael Kjörling michael at kjorling.se
Fri May 12 18:17:13 AEST 2017


On 11 May 2017 21:05 -0400, from toby at telegraphics.com.au (Toby Thain):
>>> ext2
>> 
>> That's a journalled FS, isn't it?  In which case the transactions get
>> replayed.
> 
> No, I think ext3fs was the first version that was journaled.

Correct. ext2 doesn't have journaling, but if you do `mkfs.ext2 -j` on
Linux it creates a _journaled ext2_ A.K.A. _ext3_ file system.

With the resulting selling point of ext3 being mainly _much_ shorter
fsck times.


> So was reiserfs. With pull-plug tests I could get ext3fs to toss
> cookies but not reiserfs.

ReiserFS seems to be one of those where peoples' experiences really
differ. I've had massive crashes involving reiserfs myself, but don't
think I have ever actually lost any significant amounts of data to
ext2/3. Maybe it was just bad luck, but I have been bit sufficiently
badly by it to relegate it to the scrap heap of history. At least at
the time lack of good recovery tools didn't help (but then again if
ZFS breaks sufficiently that the pool doesn't import, you're pretty
hosed, too). Backups, backups.

These days, for me, it's pretty much all ZFS where I have any say in
it, and in addition even my home desktop is on a UPS (with automated,
controlled shutdown when approaching battery depletion), so unplanned
shutdowns are far less likely to happen. About the only way that can
realistically happen is either a kernel crash, or the UPS misreporting
(overestimating) the remaining battery time, resulting in a hard
shutdown before or during the shutdown process. Neither is impossible,
of course.

-- 
Michael Kjörling • https://michael.kjorling.semichael at kjorling.se
                 “People who think they know everything really annoy
                 those of us who know we don’t.” (Bjarne Stroustrup)


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