Dhcp load testing

[Simon Hobson]

Dave C <Dhcp at gvtc.drakkar.org> wrote:

> That part about sending your logs elsewhere via syslog is extremely critical.

As a halfway house, configure syslog for async logging.
The default is (on every system I've worked on) for sync logging which as you point out means a lot of disk thrashing.

> A trick I've done in the very distant past when disk speeds were horrible was to create a virtual disk in ram (ramdisk), let the leases file live there and once a minute or so, copy the leases file to a persistent disk.

SSDs have got bigger, faster, cheaper over time. Switching to SSDs would make a huge difference - as long as the whole system supports TRIM and you make sure there's plenty of free space*.

* TRIM means that the SSD knows when a block is no longer part of a file (so it can be queued for background erasure), and having a large amount of free space gives a large buffer of free blocks for the drive to use so minimising the chance of running out at times of peak activity.