Re: How to improve performance with MDB backend?

[Quanah Gibson-Mount <quanah@zimbra.com>]

--On Monday, April 08, 2013 4:49 AM -0700 Howard Chu <hyc@symas.com> wrote:

> SaÅa-Stjepan BakÅa wrote:
> > Hi,
> >
> > Maybe this is not the best way to ask but I would like to get some
> > performance expectations or maybe suggestions how to improve
> > performance. I do have relatively long experience with OpenLDAP as a
> > precompiled package and with much less users so performance was not an
> > issue for those installations.
> >
> > Now I need to put few million users (now one million for test), custom
> > tailored schema and search performance is crucial but also modify
> > performance is big issue. Before MDB I have used HDB as backend.
> >
> > What to do to improve write part of performance or performance in general
> > (when adding data â from time to time â OpenLDAP stalls in a way)?
> > Just around 5 add/mod operations during that time then it continue with
> > much higher speed.
> >
> > I have used many different sources to find out other peoples experience
> > and I didn't choose to write to list lightly but I really need some
> > help/hints.
>
> There's nothing particular to LMDB to tune. But if you're seeing pauses
> due to disk I/O, as your iotop output seems to indicate, you might want
> to look into using a different I/O scheduler.

Not quite true.  On Linux, I suggest setting the olcDbFlags as follows:

olcDbEnvFlags: writemap
olcDbEnvFlags: nometasync

With those flags set, writes are 65x faster for me with back-mdb than they 
are with back-hdb/back-bdb.

--Quanah


--

Quanah Gibson-Mount
Sr. Member of Technical Staff
Zimbra, Inc
A Division of VMware, Inc.
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