On 11 Aug 2009, at 16:14, Grant wrote:
Josh Saddler had a couple blog posts recently about his adventures
with SSD and Gentoo:
http://blogs.gentoo.org/nightmorph/2009/08/02/ssds-and-filesystems
http://blogs.gentoo.org/nightmorph/2009/08/09/ssds-and-filesystems-part-2
I've been following those (actually posted the first link in another
thread a few days ago). It sounds like pretty exhaustive research.
The second link has removed ext4 from my "new install" list.
The posts seemed really anecdotal to me. I mean, I've got ext4 working
just fine here, so it's not really clear what he's doing differently.
Is it merely that he's using SSDs & I'm using rotating platters? He's
going back to ReiserFS, but I've had some bad experiences with that,
myself.
I'm not saying that he's wrong, but it's one bad experience. It's one
well-documented bad experience, admittedly, but a description of
"exhaustive research" (if you'll excuse me saying so) should be
reserved for tests in which they line up half a dozen systems down a
test bench, and try all the different file systems on each of them.
I wish there were some definitive way to say which filing system(s)
are safe & reliable. Mostly you're left to trust either Hans Reiser,
or Linus & his buddies (for ext[234]) or a filesystem designed for
Irix (XFS), ported over and no longer maintained by its original
designers.
I don't mean that in a bad way about XFS, because it works just fine
on one of my disks here, but choosing a filesystem is inherently a bit
unscientific and about perspective and trust and intangibles.
It's relatively easy to do performance testing on filesystems -
although we seem to see relatively few benchmarks published - but of
course it depends on what kind of data you're storing (random access
of lots of small files vs. reading through a single large file, for
instance).
It's much harder to unequivocally state how often different
filesystems get accidentally corrupted or how bad the consequences
will be when they do or how well they'll recover from it. If you put
half a dozen systems on a test bench and pulled the power plugs on all
of them mid-write, any filesystems boffin would tell you that this
test failed to consider many other possible circumstances. Should this
test be performed whilst `mv` is being performed, or `cp`? Different
file systems will probably behave differently.
So at the end of the day, all we can do is make characterisations
based on our own experience and bias and - sure - upon anecdotal
evidence like this.
When I came to Linux, ext2 was the "reliable filesystem" that was
"designed for Linux", ext3 featured incremental improvements to that
to add journalling; in those days ReiserFS was relatively new and
"racey" but "showed promise" with solid computer science behind its
technology. There is at least one former ReiserCo. employee still
maintaining & improving ReiserFS, but no longer the same dedicated
team. Now ext3 is proven - does anyone dispute that? - and ext4 is
merely "incremental improvements" to its predecessor.
So what are you going to choose? I'm sure I'm not the only person on
this list who's using ext4 just fine - in fact, I chose it because
others on this list were already using it. Here deletes of large files
are a heck of a lot faster on ext4 than on ext3.
Stroller.
