mdb expected growth

["Paul B. Henson" <henson@acm.org>]

So after updating our dev ldap environment to use mdb, and slapadd'ing a
fresh copy from our production environment into it, the database was using
828M:

Environment Info
  Map address: (nil)
  Map size: 2147483648
  Page size: 4096
  Max pages: 524288
  Number of pages used: 211612
  Last transaction ID: 1333
  Max readers: 126
  Number of readers used: 6
Status of Main DB
  Tree depth: 1
  Branch pages: 0
  Leaf pages: 1
  Overflow pages: 0
  Entries: 29

I then proceeded to run a test load on it (basically, I had a script I put
together when I added the memberof overlay that ripped through all of our
groups, removing and then re-adding all members). After this test run, the
use jumped to 1.9G:

Environment Info
  Map address: (nil)
  Map size: 2147483648
  Page size: 4096
  Max pages: 524288
  Number of pages used: 479536
  Last transaction ID: 1075380
  Max readers: 126
  Number of readers used: 11
Status of Main DB
  Tree depth: 1
  Branch pages: 0
  Leaf pages: 1
  Overflow pages: 0
  Entries: 29

There is no new data in the database, all that happened was existing data
was removed and then re-added. Is this drastic increase in space utilization
expected in such a scenario? I bumped the max size from 2G to 4G and am
rerunning the same script to see what happens.

Is there any heuristic for how mdb will grow over time, based on the initial
size from a fresh slapadd? I plan to set a fairly large maxsize, and also
monitor it with munin to keep track of any unexpected growth, but I am
curious if it is going to reach a steady-state size or continue growing over
time. I would expect growth as additional entries were added, and possibly
some growth from overhead when things were changed, but not necessarily such
a big jump in size.

Thanks.