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redzoneuser

Member

Registered: 2015-07-01

Posts: 2

how to increase and test nscd cache hit rate

Hi,
I am a young system administrator with little experience in Linux.

I'm looking for a solution to increase and test the nscd cache hit rate but I know little about it.

My 'password' and 'group' are using LDAP while 'group' is using DNS server.
I don't know so clearly how do the "positive-time-to-live" and "negative-time-to-live" impact my efficiency. For example, I don't know what the fuction of negative-time-to-live is ( in my opinion the negative record is usless) .
In my LDAP server, it has about 6000 users and 1000 groups. Our users are using these Linux computing cluster to do their simulation.
In my DNS server, it has about 4000 record of hosts.

The other question is that how can I test the cache hit rate when I change some value in nscd.conf. I know the 'nscd -g' command but how can I test the hit rate when I modify nscd.conf and clear the cache?

Thanks.

quote from http://www.novell.com/documentation/nnl … ojtia.html:
The following is a list of guidelines for the various nscd parameters.
The value of the suggested-size parameter for passwd database should be a prime number greater than or equal to 1/4th of the users expected to be used.
Increase the positive-time-to-live parameter for passwd and group database (for example to 3600 (1 hour)). Note that this might result in the cache reflecting outdated information if the eDirectory database is modified.
Increase the negative-time-to-live parameter for passwd and group database (for example to 600 (10 minutes)). Be aware that this might also result in a newly added user not appearing for up to 10 minutes, if an attempt to read that user's non-existent information was done within 10 minutes.
Increase the value of the hot-count parameter to 200. nscd will keep up to 200 entries in the cache refreshed all the time.

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,287

Re: how to increase and test nscd cache hit rate

Welcome to Arch Linux.

This is an interesting first post.  I have no idea how to help you, am an not a network administrator. 
I fear this smells a little like this might be an exercise for a student of IT.  If so, please see our policy regarding homework problems

As you are a new member I cannot look to your posting history for guidance, so I ask that you make a statement one way or the other.   If it is homework, we can still provide guidance -- it just probably will not come in the form of a direct solution

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redzoneuser

Member

Registered: 2015-07-01

Posts: 2

Re: how to increase and test nscd cache hit rate

Thanks for respond. Actually, I am a IT support engineer but not a student. Our company have about 10,000 staff and 6000 of them are using our Linux cluster to do their computing job. This' not homework.
I just want to find a way to know the relationship between the variable value and the efficiency. I need the method to find the solution.[it will be very good if someone give me the solution. ]

By the way, will someone tell me how the "positive-time-to-live" and "negative-time-to-live" work? The man page describe not so clearly.

Welcome to Arch Linux.

This is an interesting first post.  I have no idea how to help you, am an not a network administrator. 
I fear this smells a little like this might be an exercise for a student of IT.  If so, please see our policy regarding homework problems

As you are a new member I cannot look to your posting history for guidance, so I ask that you make a statement one way or the other.   If it is homework, we can still provide guidance -- it just probably will not come in the form of a direct solution