Filesystems

Shane Hathaway shane at hathawaymix.org
Thu Sep 1 22:50:47 MDT 2005


Andrew McNabb wrote:
> I've used ext2/3 for the most part, and I've never had any big problems,
> but I'm always open to new stuff.

Last year, I worked on a project that required a write speed of 50-100 
MB/s, sustained, for up to 30 minutes.  It helped that we used RAID 0 
over 4 drives, but even in that configuration the system couldn't 
sustain the required write speed.  Software vs. hardware RAID made no 
difference.  Then we experimented with filesystems.  ext2 failed pretty 
early, and reiserfs failed intermittently, but XFS passed the test with 
flying colors.  We were going to try raw partitions, but since XFS 
worked so well for this application, we never got around to it.  We also 
didn't try JFS.

Note that the XFS in SuSE's kernel (we used SLES, the "enterprise" 
version) was extremely crashy.  XFS in a vanilla kernel (2.6.8.1 at the 
time) was far more stable.  Also, I noticed that mounting a 1 TB XFS 
partition takes only a second or two, while reiserfs sometimes takes 
about a minute at that size.

(Tangent: I find Linus' kernels to be much more stable than distribution 
kernels; anyone else have the same experience?  This is contrary to the 
wisdom I hear on the net.  Maybe it's because I configure the kernel for 
specific machines rather than throw in every driver available.)

The only downside to XFS that I've seen so far is that if you run out of 
space while writing a large file, XFS drops the excess data on the floor 
and doesn't notify the application that there's a problem until the 
application tries to close the file.  That's often too late, and AFAIK 
it violates the POSIX standard.  Other than that, I really like XFS for 
large files.  I'm using it for MythTV at home.

> I've always had negative feelings towards Reiser FS, and I'm not sure
> whether it's just misguided prejudice or if it's really justified.  I've
> heard at least a couple of horror stories, and I've gotten the feeling
> that stability isn't a top goal.  Is it still this way, or has it never
> been this way, or has it improved?

I've used ReiserFS (v3) often and I can't think of any time I've lost 
data on a ReiserFS partition, even on some very flaky hard drives I have 
at work.  I've seen visibly better boot times with ReiserFS vs. ext3. 
If you use Gentoo, /usr/portage definitely belongs in a ReiserFS 
partition, because "emerge sync" runs an order of magnitude faster that 
way, compared with ext3.  Also from experience.

As always, YMMV!

Shane



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