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Re: performance very differently for two hosts that are configured identical
You are not the only one who faced this kind of problem !
2009/10/15 Zhang Weiwu <email@example.com>:
> I found the problem. Stupid problem, this took us several days!
> Since it has been so many days, I quote the full original question for
> your reference, see the bottom for the last jigsaw of the puzzle
> Zhang Weiwu wrote:
>> We have a development server 'emerson' with roughly one third of the
>> performance of our productional server 'bossdog', it runs ldap query 10
>> times faster than the productional server. I checked everything I can to
>> find out the difference, it seems both are equally configured.
>> Test method:
>> emerson:~# time for (( i=0; i<100; i++)); do ldapsearch -xD cn=manager,dc=eoa,dc=cn -w masked -b ou=contacts,ou=realss.com,dc=eoa,dc=cn '(uidNumber=7)' dn; done;
>> # zhangweiwu, contacts, realss.com, eoa.cn
>> dn: uid=zhangweiwu,ou=contacts,ou=realss.com,dc=eoa,dc=cn
>> # search result
>> search: 2
>> result: 0 Success
>> # numResponses: 2
>> # numEntries: 1
>> real 0m1.047s
>> user 0m0.320s
>> sys 0m0.352s
>> bossdog:~# time for (( i=0; i<100; i++)); do ldapsearch -xD cn=manager,dc=eoa,dc=cn -w masked -b ou=contacts,ou=realss.com,dc=eoa,dc=cn '(uidNumber=7)' dn; done;
>> real 0m41.790s
>> user 0m0.232s
>> sys 0m0.464s
>> What I have compared:
>> 1. Both server uses Debian Lenney
>> 2. Both server have same DB_CONFIG in /var/lib/ldap
>> 3. Both server have same ACL settings. In fact we tried to reduce the
>> ACL setting on the slow preforming productional server without
>> improvement result.
>> 4. Both server uses bdb
>> 5. Compare syslog at log level 256 both server produce same log messages
>> 6. The productional server shows harddisk is twice as fast as
>> development server (hdparm), free memory more than the development
>> server, and its dual-core xeon cpu should outperform the VIA CPU
>> used in the development server, yet slower. The productional
>> server average load is 0.5 which is not high for dual-CPU (with
>> hyperthreading display as 4 CPUs to Linux).
>> 7. Productional server DB is then re-built (by rm -rf & slapadd)
>> without noticeable change in performance.
>> This performance difference resulted the productional server user
>> interface much slower than user's patience.
>> What would you check further in this case? Thanks in advance
> The problem is we have been looking into openldap and system
> resource/kernel so much that we forgot other software directly related
> to performance. There had been something wrong made syslog low
> performance, change loglevel to none instantly solves the problem.