Performance Problems.. Server hardware smoked by $500 box?

John Straiton jsmailing at
Thu Sep 11 14:36:20 PDT 2003

> There's lots of tricky stuff that can be going wrong.
> I spent some time in my last two jobs (anybody got
> a new one in NJ?) on speeding up stuff like this
> and the first thing I try to do is put some kind of 
> steady-state load on the boxen and monitor each box involved 
> with  systat 1 -vmstat  .  There's one hell of a lot of 
> information there, and interactions are sometimes hard to 
> see.  If the CPU is fully occupied, it could be the network 
> stack (which will NOT show up at interrupt level) and that 
> can depend on what interface chipset you're using as well.  
> Or it could be ... well, get the data first.  If you'd like 
> to send me a few sample screens, I'll try to make suggestions 
> on what to check next.  You want to have a series from each 
> of the three configurations you're using.  And being able to 
> _watch_ what's happening on  systat  is worth a whole lot of 
> non-sequenced snapshots.
I'll take a look at this.

> Are you running firewall software on the production
> machine? 
Are you trying to hack me? *chuckle* j/k

> I don't know how the FreeBSD version will
> affect performance, but it can't help.  How about
> the reports from  top ?  What do they say?  What's
> soaking up the processor?
If you saw the two machines, rc.d/* and rc.conf are nearly identical.
There aren't any services that run on one that aren't exactly the same
on the other except the differences between the OS versions as best I
can tell. In looking at "top -qSi" (or even normal) the only things that
tend to show up at the top are httpd processes. The development machine
has the ata irq up there whereas the production doesn't seem to have
disk access in the top few entries. Just reinforcing that even with more
to do, the development machine smokes this Dell iron.

> Can you try running the back end box on a simple
> disk without the RAID in the way?  I don't recall
> all the properties of RAID 5 right now, but in general
> RAID trades disk transactions away to get disk
> throughput.  In your application, you probably need 
> transactions more than throughput.
No, it has no other interfaces configured that I could get into without
taking the machine down to hook up some cables. This thing boots of the
hardware RAID and has a cage in the front for the drives (hotswap). But
being that the RAID is one of the few things that IS the same between
production and development (the raid serves files via NFS to both
incarnations of the webserver in the same fashion) , I'd have to get an
idea why this was something I'd want to delve further into. 

> Dumb quesion: have you tried swapping cables/ports
> on the ethernet connections?  Does one link support
> jumbo frames and the other not?  How about network
> buffers: have you got enough configured, and how
> many are tied up at a time?

I'm not familiar with those configuration options but if it makes a
difference, I basically use completely default setups between the xl0
and fxp0 drivers being used in these scenarios, with GENERIC being the
kernel for all intents and purposes between both machines. Unless one
driver is set up different than the other or has inheirent speed
advantages, they should both be equivalent.

Yes, all cabling/ports and even in the case of the production machine,
interfaces have been swapped/changed. Another good idea that didn't pan

Thanks for the help!
John Straiton
Clickcom, Inc

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