Watching performance on a DHCP Server
dhcp1 at thehobsons.co.uk
Sat Feb 9 08:13:05 UTC 2008
Blake Hudson wrote:
>The pros of fsync are that I can say I will never lose a lease
>(assuming my disks don't die, RAID controller doesn't die, file
>system doesn't corrupt, RAM doesn't go bad, server doesn't hit the
Actually, for most of those, you still won't lose a lease ! The
point is, that if the write doesn't happen, then the client isn't
offered the lease.
>From a practical perspective, the thought of losing 5 seconds of
>leases in server lockup is a non-issue to me (and probably others).
Actually, I would suggest that losing leases IS a big deal and can
cause some ongoing problems (mostly with bad clients).
>If I had the choice of penalizing every request, versus penalizing a
>few requests in several years time I would choose the later.
That's the tradeoff.
I can't see any problem including a config option, provided it
doesn't appear in the config file by default, AND there's suitable
warnings in the docs (like anyone reads those !)
IIRC someone on this list did a test a while back - of the form
"throw loads of requests at the server and yank the plug, see what
happens when it comes back up". The ISC server had a lower throughput
but correctly recovered with a knowledge of what leases it had given.
A certain popular product from Redmond got through loads more client
requests (a couple of orders of magnitude IIRC) but lost loads of
them after the reboot.
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