DHCP transactions per second

Simon Hobson dhcp1 at thehobsons.co.uk
Fri Jun 15 20:05:00 UTC 2007

Ian Anderson wrote:

>  > Turn off synchronous logging in syslog. Each DHCP event may create
>>  several log entries (especially if there's a DDNS entry) and if you
>>  have synchronous logging then each log entry results in a disk write.
>What do you mean synchornous logging?  Do you mean disable logging all

No, I mean disable synchronous logging - see the documentation for syslog.

IIRC the default is that syslog will commit every log to disk before 
returning, that is synchronous logging. You can tell it to buffer 
writes, so they will go into the write queue and get written to disk 
'sometime' and in the meantime syslog returns straight away - this is 
asynchronous logging.

Synchronous logging means that if the system crashes, you will have 
very up to date logs, at the expense of performance from all those 
disk writes. Async logging improves performance (don't forget that 
the same disk block would otherwise get several writes before it is 
full) but if the system crashes then the logs on disk will not be as 

You make logs async by putting a '-' before the file name in 
syslog.conf, eg "-/var/log/messages"

More information about the dhcp-users mailing list