OpenLDAP MDB backend for riak

Howard Chu hyc at
Mon Oct 15 10:10:02 EDT 2012

Kresten Krab Thorup wrote:
> Howard,
> I took a look at MDB, and it does look quite promising!
> Perhaps you can enlighten us a bit on these aspects of MDB:
> - How do you back up an MDB instance? Can you do that while it is actively
updating, or do you need to stop it? I'm asking because the operational ease
of the log-structured stores is one of the features that many Riak'ers like
quite a lot.

The current mdb.master branch in git now has an mdb_env_copy() function for 
making a backup of an MDB instance (live or not). Also an mdb_copy program for 
invoking it.

> - What is the typical response-time distribution for inserts? I've tried
> to
work with BDB some time back, and one of the issues with that is that every
once in a while it slows down quite significantly as B-tree rebalancing makes
some requests unreasonably slow.

This post on memcacheDB with MDB may be illuminating:

You can see the response time distribution for BerkeleyDB 4.7, MDB, and the 
original Memcached 1.2.0 code on which MemcacheDB was based. An interesting 
data point is the 4-threaded case, in which MDB average reads are faster even 
than the pure-memory memcached and overall runs with much faster maximum 
duration and much narrower variance.

   -- Howard Chu
   CTO, Symas Corp. 
   Director, Highland Sun
   Chief Architect, OpenLDAP

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