[openssl-users] LMDB use of sparse or non-sparse data file

Geoff Swan gswan3 at bigpond.net.au
Sat Mar 21 23:47:51 UTC 2015

I had to duplicate an LMDB database for replication recently, and used
mdb_copy to do so.
One server is using the original data.mdb database (which is sparse) and
the other is using the mdb_copy non-sparse data.mdb file.
The two servers are identical (hardware, OS, software and
configuration). OpenLDAP-2.4.39 is being used, 64 bit Linux OS.
mdb_stat shows the map size as the same, which is expected.

Will the use of the non-sparse file cause any performance issues?

The reason for asking is that I am seeing a difference in search times
between the two.
With 20 million objects, a search on modifyTimestamp (which is indexed)
server 1: approx 1s
server 2: approx 60s

server 2 started with the same search time as server 1 when the
databases were originally copied, but has slowly increased its search
time over about a week for this same search.

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