Disk I/O Performance

[João Carlos Mendes Luís]

     I'd say that you have to check which CCD chunk size is best for 
your needs.  The manual for vinum recommends avoiding chunk sized to a 
power of two, which is probably the first big mistake of everybody.

     Try mounting with option noatime, if you haven't already.  And use 
the largest block size possible when formatting.  Last time I read about 
there was a limit of 16384, but I would expect better performance for 
large file with 64k blocks (and 8k frags).

     If you don't have a need for safety on the files, you could try 
mount async and measure if it suits better you need for performance than 
softupdates.  Sometimes softupdates is faster, and it is always safer.

Kristofer Pettijohn wrote:

> Im looking for some suggestions on I/O performance.
> 
> I'm using FreeBSD 4.10-RELEASE on a Usenet transit server running
> Diablo for the transit software.
> 
> I have 4 Seagate ST373435LC SCSI drives, 70GB each, and I am using
> CCD to bind them together with RAID-0 stripes.
> 
> I can pull in anywhere from 30-40 MB sec and push out ~ 8-15 MB/sec..
> averaging about 50 MB/sec throughput.. feeds coming in are coming
> in just fine, but sending stuff back out is lagging behind.. its
> falling about a half hour behind every hour.
> 
> I've used tunefs to set the average file size to 20 MB and enabled
> soft-updates, as these are generally larger binary files that just
> get appended to, and then seeked later on to send the article out,
> I've played with setting the stripe size from anywhere between 8MB
> and 64MB, and did not see much change on performance between those.
> 
> Maybe I'm just missing something small, but on these SCSI drives
> which have 160 MB/s transfer rates, I'm expecting a bit more than
> I'm getting with CCD.
> 
> Can someone give me any pointers to look at or suggestions of things
> to try?