[linux-audio-user] is ext3 ok for real-time / low-latency?

[Jan "Evil Twin" Depner]

I have copies of Mark Knecht's benchmarks on my web page :

 http://myweb.cableone.net/eviltwin69/Arcana.html

as well as a write-up explaining why you shouldn't use ext3.  It
basically comes down to the fact that ext3 is using a separate file to
handle the journal.  What this means is that as you write your audio
data, every once in a while, the system has to write to a different file
in a separate location on the hard drive.  It will depend on how close
the files are physically to each other, disk latency, and a host of
other things but, eventually, you will see problems with ext3.  It's not
hard to convert to reiserfs (instructions (destructions?) are included
on the above page) so why not.  Reiser journals are kept with (as part
of?) the files - you don't have to run fsck after a crash.  A real
intersting thing to note is that reiserfs actually seems to be faster
than ext2 for what we're doing.

Jan

On Sat, 2003-02-15 at 06:47, Frank Barknecht wrote:
> Hallo,
> Larry Troxler hat gesagt: // Larry Troxler wrote:
> 
> > Well, since my installation (mostly RedHat 7.1) was getting to be a big mess, 
> > with bits and pieces from different places, I decided the best way to get a 
> > working C++ compiler was to get a new drive and do a fresh redhat 8.0 
> > installation :-)
> > 
> > My immediate question: is ext3 bad news for real-time work? I saw some 
> > linux-audio-dev list messages from people who were having freezes using it.
> 
> I didn't get any freezes with ext3 and all my audio work (jack, Pd,
> MusE).
> 
> > Should I convert my filesystem back to ext2 (assuming there is a way) or not?
> 
> It still is ext2 somehow, because you can mount ext3 filesystems as
> ext2 as well. But you can reconvert, I think. 
> 
> > Which one in theory (assuming no bugs which seems to be the cause
> > for the freeze) should be better for low-latency work?
> 
> This seems to change as ext3 evolves. There was a time when it was
> faster, currently it seems worse than reiserfs. But I have a lot of
> trust in ext3 and I hate having to wait for minutes on e2fsck clean up
> after a crash, so I will keep running ext3 instead of reiser or ext2.
> 
> I didn't benchmark it, but maybe you can find some on the net.
> 
> ciao
> -- 
>  Frank Barknecht                               _ ______footils.org__