Performance Problem Postmortem

[sthaug at nethelp.no]

> Things you can do :
> Make syslog asynchronous - that removes one synchronous write to 
> disk. By default it's sync and that means another hardware write 
> before the call returns.

As an aside, this problem is Linux-specific, as far as I know. It's a
pretty bad default. BSD-based systems do not have synchronous syslog
writes by default, nor does Solaris as far as I can remember (been too
long since I worked with Solaris on a regular basis).

> If you are brave, or have suitable battery backed hardware, put the 
> leases file on a ram disk. It must not be on a 'normal' ram disk that 
> would be lost in a system crash or power failure as that would leave 
> you without a lease file. Generally look at the performance of your 
> disk system as that will be a limiting factor on response rates.

Leases file on some sort of battery backed RAM disk or RAID is a key
feature, definitely.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no