Re: Recommended SLAPD cache sizes

[Paul Whitney <paul.whitney@xxxxxxxxxxxxxxxxx>]

Hi Mark,

What I was referring to is:

"nsslapd-cache-autosize-split

The value sets the percentage of RAM that is used for the database cache. The remaining percentage is used for the entry cache.

More than 512 MB RAM database cache do not improve the performance. Therefore, the database cache is limited to 512 MB." - https://access.redhat.com/documentation/en-us/red_hat_directory_server/10/html-single/performance_tuning_guide/index#tuning-dbs-for-searches

Then further down is a table that tops off at 512MB for dbcache in the same document.  But even further down it contradicts by suggesting the results of the dbmon.sh script can provide insight into how much more the dbcache can be to improve performance with the 2.2% free example.

All these tuning features are great, but gets confusing when trying to mix and match the best combination of settings.  

I did go over your recommendations and have settled for now on increasing the dbcache to 5GB.  Our consumers are configured with 64GB and the masters 128GB.  While the percentage of free space in the dbcache is not optimal (more than 12%), we are achieving a hit ratio of 99%.  

Paul M. Whitney, RHCSA, CISSP
Chesapeake IT Consulting, Inc.
2680 Tobacco Rd
Chesapeake Beach, MD 20732 

Work: 443-492-2872
Cell:   410.493.9448
Email: paul.whitney@xxxxxxxxxxxxxxxxx

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From: Mark Reynolds <mreynolds@xxxxxxxxxx>
Sent: Tuesday, July 16, 2019 9:30 AM
To: General discussion list for the 389 Directory server project.; Paul Whitney
Subject: Re: [389-users] Recommended SLAPD cache sizes

 

Hi Paul,

On 7/16/19 9:16 AM, Paul Whitney wrote:

Is there some formula or recommendation on determining what would be the optimal cache settings for a directory server (389-ds of course) with following sizes? I looked at the DS 10 Admin Guide online and am getting conflicting information.  But the manual shows a table and suggests that the max size for the cn=config dbcache is 512MB.

There is no limit on the cache size value besides what you are limited to by a unsigned long integer.  Do you have a link to where it says 512 MB is a maximum?

  But I tried with 5GB and it appears to work fine with it, although over time start to see negative values (prob not enough cache) and roevicts while running the dbmon.sh script.

__db files = ~6GB

groupRoot = 1.5GB

userRoot = 20GB

What values would yield best performance for:

cn=config dbcache? currently set to 5GB but are still seeing lots of roevicts. As much 

userRoot entry cache? currently set to 21GB (hit ratio so far at 95%)

groupRoot entry cache? currently set to 2GB (hit ration so far at 96%)

Virtual machine configured with 8CPU, 128GB RAM. Load is in the low 20's with occasional spikes to high 20's.

If you have 128 GB available to you then I would continue to increase the cache sizes until you get to 99% hit ratio for the two entry caches, and the db cache.  Also make sure the DN and NDN caches also have a 99% cache hit ratio:

https://access.redhat.com/documentation/en-us/red_hat_directory_server/10/html/performance_tuning_guide/tuning-dn-cache

https://www.port389.org/docs/389ds/design/normalized-dn-cache.html

I would also look into running the DB on a RAM disk since you have the resources to do so:

https://access.redhat.com/documentation/en-us/red_hat_directory_server/10/html/performance_tuning_guide/tuning-db-cache#db-cache-on-ram-disk

HTH,

Mark

Paul M. Whitney, RHCSA, CISSP
Chesapeake IT Consulting, Inc.
2680 Tobacco Rd
Chesapeake Beach, MD 20732 

Work: 443-492-2872
Cell:   410.493.9448
Email: paul.whitney@xxxxxxxxxxxxxxxxx

CONFIDENTIALITY NOTICE 
The information contained in this facsimile or electronic message is confidential information intended for the use of the individual or entity named above. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this facsimile message to the intended recipient, you are hereby notified that any dissemination, or copying of this communication is strictly prohibited. If this message contains non-public personal information about any consumer or customer of the sender or intended recipient, you are further prohibited under penalty of law from using or disclosing the information to any third party by provisions of the federal Gramm-Leach-Bliley Act. If you have received this facsimile or electronic message in error, please immediately notify us by telephone and return or destroy the original message to assure that it is not read, copied, or distributed by others.

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