Re: Kudos to all who contributed to MDB

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

--On Wednesday, September 18, 2013 2:01 PM -0600 Brent Bice <bbice@sgi.com> 
wrote:

> On a SLES11 system, for instance with the 2.6.32.12
> kernel

This is because the SLES folks seem to love to seek out ways to break 
things for servers.  I'm not really sure why they call themselves an 
"enterprise server" product anymore.  It is trivial to fix this:

ulimit -v unlimited


>     On a newish ubuntu system with a 3.5 kernel this doesn't seem to be
> an issue - tell OpenLDAP to use whatever maxsize you want and it just
> works.  :-)

There's a known issue in 3.0 through 3.9 kernels that is fixed in 3.10 that 
will affect your write speed with mdb.  See:

<http://www.openldap.org/lists/openldap-devel/201309/msg00008.html>

I have 3.10 running on my Ubuntu12 box now, it is a significant 
improvement.  It also appears this breakage was backported on some Linux 
OSes into their 2.6 kernels.


>     I'd also only use MDB on a 64 bit linux system. One of the other
> headaches I remember running into with memory mapped I/O was adding in
> support for 64 bit I/O on 32 bit systems.  Best to avoid that whole mess
> and just use a 64 bit OS in the first place.

Correct.

>     Anyway, thanks again to everyone who contributed to MDB. It's lots
> faster than BerkeleyDB in all of my testing so far. 'Looking forward to
> gradually shifting more of my LDAP servers over to it.

For me, the back-mdb write speed is about 50x to 70x faster than the BDB 
based backends.

<http://wiki.zimbra.com/wiki/OpenLDAP_MDB_vs_HDB_performance>

Also quite a bit faster for reads:

<http://mishikal.wordpress.com/2013/05/16/openldap-a-comparison-of-back-mdb-and-back-hdb-performance/>

Glad to hear MDB is working out well for you!

--Quanah

--

Quanah Gibson-Mount
Lead Engineer
Zimbra Software, LLC
--------------------
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