On 2010-01-06T16:32:33, Dejan Muhamedagic <[email protected]> wrote:
> > That said, I'm fine with using a file if it keeps up the performance.
> > But the sync_script - we definitely don't want to be calling an external
> > script, I guess. csync2 would be automatic anyway.
>
> The script (or program) is invoked once in a while on monitor,
> shouldn't be a performance issue.
It's invoked every time, and to keep the connection table reasonably
uptodate, I guess monitor would be scheduled fairly frequently.
So yes, this is costly, the question is whether it is still good enough
;-) In particular over drbd, it'd be good to see a test and establish
what a reasonable limit is.
> > Oh. This is quite costly, is it not? Scanning the full TCP connection
> > table and regenerating the whole lease-file?
> Looking again at it, egrep and while loop could be replaced by a
> perl/awk/python snippet. Then it should be fast enough.
We're looking at scanning potentially thousands of connections here,
which a busy file server might easily have. There's not just the
processing overhead in user-space, but also the overhead of retrieving
the information from the kernel, and I doubt that that is extremly fast.
Worse, scanning those tables might even incur an in-kernel penalty due
to data structure locking.
But that's just a gut feeling, I'd be happy to see some numbers.
> > Is there really no interface by which we can be notified when TCP
> > connections get established and deleted?
> In that case we need a daemon to take care of the connection
> table. That would obviously be a more elegant solution, but I'm
> really not sure if it's absolutely needed. This machinery seems
> good enough to me. At least let's first see how it behaves in
> some busy environment.
Yes, and that's why I'd like to see some numbers ;-)
> > How is this done in Samba?
Further, has there been some communication with say the netfilter group
or the internal Labs kernel team as to how to get at that state?
I'm not saying the current approach is bad, I just want to understand
why it is good enough ;-)
Regards,
Lars
--
Architect Storage/HA, OPS Engineering, Novell, Inc.
SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg)
"Experience is the name everyone gives to their mistakes." -- Oscar Wilde
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