nscd and nscd.conf

nscd and nscd.conf

Post by Ed Oak » Tue, 05 Jan 1999 04:00:00

I have an E3000 running Solaris 7.  This password file
contains about 11,000 users.  The nscd process seems to consume
a large amount of CPU time.  I called Sun to see if there were any
suggestions for tuning nscd with the nscd.conf file, and they provided
no information.  The manual pages do provide information but no good
suggestions as to which changes might enhance performance.

Are there any rules or guidelines for configuring this process or
do I have to live with the amount of CPU time it consumes?

#  Ed Oakes                         #        
#  Radford University               #        Office  Walker 155

#  http://www.runet.edu/~clientse   #


nscd and nscd.conf

Post by Greg Andre » Thu, 07 Jan 1999 04:00:00

>I have the following set in /etc/nscd.conf on a Solaris 2.5.1 box
>with 15000 mail users.

>        positive-time-to-live   passwd          600
>        negative-time-to-live   passwd          5
>        suggested-size          passwd          509
>        keep-hot-count          passwd          50
>        old-data-ok             passwd          no
>        check-files             passwd          yes

Mine, for a U1 serving 12000 users, though only 6000 connect on any
particular day:

        positive-time-to-live   passwd          1800
        negative-time-to-live   passwd          60
        suggested-size          passwd          4001
        keep-hot-count          passwd          100
        check-files             passwd          yes
        old-data-ok             passwd          yes


>The hashed value "suggested-size" has to be a prime number or some weirdness.
>I found that raising this setting fixed up a lot of problems Eudora POP3 users
>were having with timeouts.

Yes, indeed.  I did something similar on my POP server.  The questions
I hoped the manpage/answerbook/docs.sun.com would answer about nscd
parameters were:

  1. How should the suggested-size parameter be scaled?  Should it be
     the prime number just above the number of often-looked-up passwd
     entries?  Should it be more than twice that number, as in the
     hash tables found in other applications?  What's more important,
     the total size of /etc/passwd, or the number of entries looked up
     during the day/hour/minute/positive-time-to-live?

  2. How big can the dataset become before it starts to slow nscd down?

  3. What parameters have the most direct effect on memory consumption?
     Are there statistics dumps available from nscd that can be used to
     discover when the time-to-live or keep-hot-count parameters are too
     large or too small?

The answers to these questions are essential for anyone who wants to
tune nscd's caching.  Also, I've found nothing, though I haven't checked
the Porsche book or the various magazine columns yet.


>                       The downside was that nscd now grows to awesome
>size, consuming all memory after a few weeks, especially during times of
>extreme usage.

I have a cron job that kills and restarts nscd every morning around 4am
to release the memory consumption.  Since it's critical to the operation
of my POP server, I also have a cron job running every 3 minutes that
detects when nscd has died, restarts it, and logs a message.  Highly



1. Solaris 9: nscd and nscd.conf - High cpu use.

I have a server that ncsd daemon run and it process causes a elevation
cpu's use, but the sum from cpu usage in top command isn't  100%  and
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This problem happen in solaris 9 and nscd.conf is default file.

Let me know:
How configure nscd.conf to the better performance according to
statistics from output "nscd -g" command?


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