DHCPD performance -- solid-state disks?

Jason Antman jantman at oit.rutgers.edu
Fri Sep 9 15:20:13 UTC 2011


We had similar problems a year ago when we started using our central 
DHCP servers for wireless client leases. We're running dhcpd 4.2.0 on 
CentOS 5.5.

We moved everything (config file, log file, leases file) to a 500MB 
ramdisk. Our init script is modified so that it persists ramdisk 
contents to HDD on start/stop/restart, and we also modified our 
system-wide init scripts to do the same thing. I don't remember the 
numbers offhand, but this got us many orders of magnitude better 
performance. I don't think that SSD is really required, IMHO.

-Jason Antman
Rutgers University

John Hascall wrote:
> All,
> We are starting to see our dhcpd server unable to cope with
> our peak load (the top of the hour when students move from
> one building to another).   Ideally, our wireless infrastructure
> would allow them to keep their address as they roam, but this
> is not the case, so we see large surges in lease-swapping during
> these 10 minute periods.  It looks like we can do about 50/second
> with our current hardware.  The CPUs are never above a few percent
> busy, so my belief is that we are limited by our synchronous-write
> speed to the lease file.  Does this seem correct?
> We are currently using mirrored 15k SAS drives.  Is our best
> move to go to solid-state disk?
> Thanks for any advice you might have!
> John
> _______________________________________________
> dhcp-users mailing list
> dhcp-users at lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users


Jason Antman
System Administrator
Rutgers University
OIT Central Systems & Services / NetOps

Office: 732-445-6363
Cell: 732-983-7256
jantman at oit.rutgers.edu

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