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Re: PSINet/Cogent Latency

  • From: Richard A Steenbergen
  • Date: Tue Jul 23 02:12:02 2002

On Tue, Jul 23, 2002 at 01:56:45AM -0400, Phil Rosenthal wrote:
> 
> I don't think RRD is that bad if you are gonna check only every 5
> minutes...

RRD doesn't measure anything, it stores and graphs data. The perl pollers
everyone is using can barely keep up with 5 minute samples on a couple
dozen routers and a few hundred interfaces, requiring "poller farms" to
be distributed across a network, 'lest a box or part of the network break
and you lose data.

> Again, perhaps I'm just missing something, but so lets say you measure
> 30 seconds late , and it thinks its on time -- So that one sample will
> be higher , then the next one will be on time, so 30 seconds early for
> that sample -- it will be lower.  On the whole -- it will be accurate
> enough -- no?

"enough" is a relative term, but sure. :)

> I'm not saying a hardware solution can't be better -- but it is likely
> overkill compared to a few cheap intels running RRD -- assuming your
> snmpd can deal with the load...

What hardware... storing a few byte counters is trivial, but polling them
through snmp is what is hard (never trust a protocol named "simple" or
"trivial"). Creating a buffer of samples which can be periodically
sampled should be easy and painless. I don't know if I call periodic ftp 
"painless" but its certainly a start.

-- 
Richard A Steenbergen <ras@e-gerbil.net>       http://www.e-gerbil.net/ras
PGP Key ID: 0x138EA177  (67 29 D7 BC E8 18 3E DA  B2 46 B3 D8 14 36 FE B6)