hardware requirements per hits
Bill Larson
wllarso at swcp.com
Mon Aug 17 15:59:48 UTC 2009
Alans <batpower83 at yahoo.co.uk> said:
> @Matus: let me put it in this way, if I want to create a budget for next
> year for example, then I should know what upgrades I need for next year
> (estimated needs), and let's assume dns queries increase monthly by x hits,
> now, if I know how many hits will make me upgrade cpu and memory then I can
> find out my cpu and memory needs for next year, hope this explain to you
why
> my question is not "usless", at least for me.
> I'll be happy if you tell me another way to know my needs for next year.
I won't necessarily go so far as to say this question is useless, but it is
almost impossible to answer.
You aren't telling us what you current situation is; what you are seeing for
a query load, whether you are running a server for authoritative data or a
resolving server, if you are using DNSSEC, etc. This is to say nothing
about your current hardware; CPU, memory, network/Internet connectivity,
etc. Also, are your running anything else on the same platform as your DNS
server?
My best suggestion is to test your environment yourself. Run "queryperf"
(or, Nominum's "dnsperf", for authoritative servers, and "resperf", for
caching resolvers, tools) to determine what sort of level your servers can
support. Then, compare this result to the level of service that you are
currently seeing. This will give you an idea of what level of service your
systems can provide. If the maximum performance cannot meet your
expectations, then you need an upgrade. If they do meed your expectations,
then you are ok. Simple enough.
But, some questions that only you can answer for your situation. Who is
querying your server? What queries are you currently receiving and
answering? How are your servers currently performing? What is the bottle
neck that you are seeing? Is it CPU? Memory? Disk I/O? Network?
(Bottleneck is sort of a bad term here. A better phrase is "What part of
the system is limiting your performance?") How long does it take for your
server to completely start AND is this a problem for you? (More zones, and
large zones, makes for a slower startup. But, if it starts fast enough for
you then it is acceptable.)
I used to run a major DNS server on a microVAX II handling 500 queries per
second (a LONG time ago). BIND doesn't necessarily require much CPU. It
can require lots of memory. (And if you are running other services on the
same system, then these other services have to share memory with your DNS
server.) Rarely, is disk I/O an issue, unless you are seeing excessive
swapping/paging, which says you need more memory. Network or Internet
connectivity isn't normally an issue either (DNS traffic doesn't have to be
excessive if your systems are reasonably configured.) If you are using
DNSSEC, or are planning on it, you can expect to use more CPU.
Again, all of these things are things that you can determine yourself by
testing your server performance. I remember a quote from somewhere a long
time ago. "If you don't know how your system is running now when things are
good, how do you expect to be able to say what is causing a problem in the
future when things are bad?" (I suspect that this cam from "System
Performance Tuning" by Mike Loukides, O'Reilly & Assc. My copy is quite old
but still useful.) Know how your system is performing BEFORE there is a
problem.
Bill Larson
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