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I'm facing really slow speed serving just static files from 300 to 900 MB on a 1 GBps dedicated line.

This is the output from iostat but I don't know if this is ok or not.

Linux 2.6.32-220.13.1.el6.x86_64 (zlin) 05/04/2012 _x86_64_ (4 CPU)

avg-cpu: %user %nice %system %iowait %steal %idle 0.36 0.00 2.70 35.74 0.00 61.19

Device:   rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda          7.53    17.90   97.65    0.76 26641.93   149.18   272.25    22.72  230.85   7.46  73.39


netstat -an |grep :80 |wc -l

iptraf shows 165000 KB/s

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The right answer here is to compare these stats against what your system looks like when it's functioning normally. The importance of getting a baseline for performance analysis can not be overstressed.

Nevertheless - there a few good tutorials on iostat:

So with those refreshers, let's take a stab: - your disk are busy, but not to capacity: utilization is 73% - disk requests are getting serviced in ~7ms, which sounds pretty good - most tellingly: CPU is largely idle (61%), and otherwise waiting for I/O.

I'd say there's likely something else getting in the way, maybe delaying/buffering the request to begin with. Might be worth trying to measure -- if possible -- just one httpd process serving one big file, and see if the picture looks different.

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