Linux bind / dhcp iowait status

Tom Greaser tgreaser at
Wed Mar 15 19:30:50 UTC 2006

its a dhcpd / dns / mysql local dbase / and apache (last two for
management purposes)

SORRY my bad .. i did have phones set to 5 days...

Thanks.. I was thinking that was kinda high!!!

we have had issues with the hardware mirror before.. and
of course after the fact.. thats when i started getting
sar checks for this kind of data..

I do have 
 update-optimization false;

the way i rehup dhcpd and dns .. it 
overwrites the ddns info.
this way the clients when renewing their leases
will also do a ddns update request.

ls -al dhcpd.leases
-rw-r--r--  1 root root 2515836 Mar 15 14:26 dhcpd.leases
 sleep 60
 ls -al dhcpd.leases
-rw-r--r--  1 root root 2535524 Mar 15 14:28 dhcpd.leases

diff = 19688  (19k)

>>>dhcp at 03/15/06 12:06 pm >>> 
Tom Greaser wrote: 
>have a beefy box that shows 18.40 % iowait at PEAK times 
>and as low as 5.50 % during work hours.. 
>have 2000 phones lease set to 1 day 
>2000 pc lease set to 4 hours.. 
>running ddns on this host ... 
>just wanting to see if this is "normal" 
>will track down to see if its named or dhcpd doing the bulk of IO
>Its an Redhat AS 4 update 3 box with mirrored scsi Ultra 320 drives 
>10000 rpm 
>from free -h 
>buffer 137meg       cache 1627 meg 
That sounds exceedingly high IF the box is only doing DHCP and DNS. 
In fact I'd consider 5.5% to be exceedingly high for such a box. 
What else is running on the box ? 
Does it make any difference if you increase lease times as Glenn
suggests ? 

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