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Performance in Linux-AD Integration Scenarios

A reader kindly shared with me some tips and tweaks he used to help resolve some performance issues with Linux-AD integration, and now I’d like to share them with you:

I ran into some nagging performance issues with Linux/AD integration the other day, and managed to solve them (mostly)—I thought you might be interested in the solution.

Since I’m not exactly following your integration guide (I use DNS lookups to locate LDAP servers in AD, and use GSSAPI authentication for nss_ldap instead of a binddn), I have a bit more overhead on my getent system calls, that was starting to get noticable when it came to getting directory listings, etc.

Two things I have done to alleviate this issue:

  1. Since we have a flat catalog, and all of our DCs are also GCs, I disabled recursion. This is not universally relevant, but it does assist me

  2. I edited /etc/nscd.conf to set a 5 minute cache time for passwd and group (but not host!) entries. Data is still usually piping fresh, but now we only call nss_ldap once every 5 minutes, instead of every time we need to know who owns a file. Then I started nscd, and set it to start on boot.

NSCD is a standard part of most RHEL and derivative installs.

Since implementing the above, the user-level experience is no longer discernably different than the old /etc/passwd method of authentication/authorization.

This is good information to have. Thanks to Brandon for sharing his experience!

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