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From Josh Wyatt <josh.wy...@hcssystems.com>
Subject [users@httpd] Re: High performance apache logging
Date Wed, 05 Jan 2005 21:23:22 GMT
Axel-Stéphane SMORGRAV wrote:
> What do you mean by system load? Is it CPU utilisation or the number of processes waiting
for the CPU including those waiting for I/O?
> 
> In any case, I would be very surprised if adding processing of Perl scripts to the equation
would improve performance...
> 
> You most probably have a disk I/O performance problem. That can be solved by investing
in faster disks (SCSI in stead of ATA, for example), or doing striping on multiple disks (RAID0).
You could even do striping across disks on different controllers.
> 
> You did not say what kind of systems you're running.
> 
> -ascs

There are a fair number of processes; I will have to get back to you on
specifics.  We get probably 1 million hits per day per server; and 90% of those
are between 7am and 5pm.  Generally about 25-30 reqs/second.

These are IBM blade servers.  They each have dual 146GB 10k RPM disks in
hardware RAID1. Each server has dual 3.2ghz xeon CPUs, and 4GB memory.  There
are 4 servers.  We're running RedHat AS 2.1, and Oracle's apache (a 1.3.x
derivative).

One thing of note, they all run SSL.  The ssl_session_cache is of type "dbm",
and ssl_mutex is of type "file".  I have also considered that there could be
contention on these files as well.

I'm lead to believe we're I/O bound because of iostat output which shows average
wait times greater than 100ms, and they're all writes:
Device:  rrqm/s wrqm/s   r/s   w/s  rsec/s  wsec/s avgrq-sz avgqu-sz   await
svctm  %util
sda7       0.00  39.00  0.00 60.00    0.00  816.00    13.60     9.30  155.00
63.33  38.00


(sda7 is the partition where the logfiles, ssl_session_cache, and ssl_mutex reside)

This frequently pushes the system CPU utilization higher, raising the load average.

I feel the disks subsystem is pretty fast, but sometimes fast is not fast enough
:).  I intend to temporarily shutdown logging on two of the four machines and
study the effect.

Thanks,
Josh

> 
> -----Message d'origine-----
> De : Josh Wyatt [mailto:josh.wyatt@hcssystems.com] 
> Envoyé : mercredi 5 janvier 2005 16:54
> À : users@httpd.apache.org
> Objet : High performance apache logging
> 
> Hi all,
> 
> I'm interested in hearing anyone's thoughts on better performing logging mechanisms for
apache.  My environment consists of four servers, load-balanced using round-robin DNS (which
works very well).  We are currently logging using just the standard local file logging, and
it is pushing system load pretty high due to our load.  I'm leaning toward something using
a perl script, a big logserver, and pipes...?
> 
> Thanks in advance,
> Josh
> 
> 
> 
> 
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