improving concurrency/performance

[Paul Dekkers]

Hi,

Andrew Morgan wrote:

> On Sun, 6 Nov 2005, Michael Loftis wrote:
> 
>> I'd also be VERY interested since our experience was quite the 
>> opposite. ReiserFS was faster than all three, XFS trailing a dismal 
>> third (also had corruption issues) and ext3 second or even more dismal 
>> third, depending on if you ignored it's wretched large directory 
>> performance or not.  ReiserFS performed solidly and predictably in all 
>> tests.  Not the same could be said for XFS and ext3.  This was about 2 
>> yrs ago though.
> 
> Make sure that you format ext3 partitions with dir_index which improves 
> large directory performance. 

... but decreases read performance in general... at least that is what I 
found under RH / Fedora!
Look at:

http://www.surfnetters.nl/paul/fs/2/read.png
http://www.surfnetters.nl/paul/fs/tarcopy-read-ext3.png

... to see that reading from ext3 with dir_index enabled takes about 
2h15 to read 20 Gb of mail data, while...

http://www.surfnetters.nl/paul/fs/read-plainext3-reiserfs.png
http://www.surfnetters.nl/paul/fs/2/read2.png

... without dir_index it takes only 15 minutes! ReiserFS was a bit 
slower for me with reads, but faster in writes. ReiserFS was also 
predictable in writes, where ext3 was slow(er) on large directories, but 
not that dramaticly. (I have graphs of that too.)

http://www.surfnetters.nl/paul/fs/2/write.png

BTW: I found that chaning dir_index with tune2fs didn't work as 
expected. If I disabled the dir_indexes, even after a forced fsck, 
performance was still slow. Enabling didn't give predictable results 
either: I had to specify it with mkfs.

I posted this to the RedHat list once, no-one replied. I decided that my 
tests where satisfied my questions for what fs to use under RedHat 4 for 
our NG mail platform... (ext3: supported, lots of (coroner) tools, fast 
enough, available in the stock kernel (if you need RH), ... and ReiserFS 
3 already has a successor, ...)

Paul

P.S. I also compared FreeBSD's UFS2 under 5.3. I should maybe try again 
with 6, since that release should have improved filesystem and disk 
performance in general. We use FreeBSD now, it's a pity we move to RH 
for this, but "Dell hardware" maybe says enough.

P.S. You can look at the graph's including some comments on
http://www.surfnetters.nl/paul/fs/2
and
http://www.surfnetters.nl/paul/fs
(more rubbish)