RE: ext3

["Mark Knecht" <markknecht attbi com>]

Grendel,
   Thanks for the pointers. Both reiserfs and XFS look interesting to me,
although there are two issues that I'm not clear about vs. the simple
solution we have with ext2 - PCI bus overhead and latency.

   If ext3, for instance, is just ext2 with journaling, then what percentage
overhead do I have on the PCI bus running ext3? How many journal reads and
writes take place vs. data reads and writes? Also, since the journaling is
on the same drive, this causes the drive head to seek to some other
location, which then means it has to seek back to get data. What sort of
overhead does that entail?

   I know absolutely nothing about reiserfs or XFS, but I'd certainly want
to better understand those issues. The 'large' file sizes on the page you
pointed at below are really less than one second of audio at 96KHz. All
indications are that these file systems would be an improvement, if they
don't have some sort of latency issue. That can be tested using programs
we're running on the low latency kernels.

   Thanks for the pointers. I'm going to set up a partition of each type and
try to check them all out over the next month or so.

With best regards,
Mark

-----Original Message-----
From: redhat-install-list-admin redhat com
[mailto:redhat-install-list-admin redhat com]On Behalf Of Kalum /
Grendel
Sent: Monday, September 30, 2002 5:27 PM
To: Mark Knecht
Cc: redhat-install-list redhat com
Subject: RE: ext3


On Mon, 30 Sep 2002,  Mark Knecht commented thusly,

> Grendel,
>    Is there any technical information to compare the speed of these file
> systems? I'm working on low latency audio stuff where the speed and
> reliability of the file are really important. I'd like to be able to see
> some data.

Okay Mark I refreshed my memory and herei s what I came up with,

<http://bulmalug.net/impresion.phtml?nIdNoticia=642>

They say that reiserfs is faster for reading small files, but for larger
files >16k then XFS is better.

basically hans reiser (authour of reiserfs has done his own becnhmarks)
and they are here....(bear in mind that they may be biased ;-)

<http://www.informatik.uni-frankfurt.de/~loizides/reiserfs/oldpage/ext2-reis
erfs-xfs.html>

Now for my own two cents, considering your problem there are certain
things we know for certain.

1. You need a journalling file system whcih is reliable and fast.
So that automatically excludes ext2 or ext3, ext3 is buggy and slower than
ext2, as any journalling system is slower than the non journalling
varient. So ext3 is out and good riddance I must say.


2. So that leaves you with a choice of XFS or reiserfs. Well my favourite
personally is XFS, but what I would say is that fmo my experience and the
benchmarks it apppears that reiserfs appears better for a large amount of
small <16k files, but if you are dealing with large files, ie media
streaming etc, then XFS appears to be better.

Basically it appears that both reiserfs and XFS are good file systems with
minimal differences and I agree with it.

So Mark you can try out both or whatever you prefer and see.

Personally I have been using XFS it makes a excellent recovery in spite of
numerous power outages I havent lost any data, its recovery is a few mili
seconds etc, its reliable.

The downside of XFS is that you need to patch ther kernel from patches
available at SGI's XFS site.

So you could try reiserfs and see first as it appears to be easier, ie
redhat shold have reiserfs as a module at least in the kernel.

The bottom line of all the benchmarks is that ext3 fails horribly when
compared to XFS or reiserfs, and rightly so just see how many people have
problems with it (poor reliability), the only reason redhat is hoisting
ext3 is because the person who develop it is a redhat employee, so we end
users have to have this garbage stuck down our throat.

Lets face it ext2 was slow enough, so you can imagine how slow a
ext2+journalling (ie ext3)would be :-)

Best Wishes,
Grendel


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