Sleepycat and hash functions

[Hallvard B Furuseth <h.b.furuseth@usit.uio.no>]

http://www.openldap.org/faq/index.cgi?file=756 says one can use BDB's
db_dump utility for on-line backups while slapd is running.
However, db_dump's manpage says:

  Dumping and reloading Hash databases that use user-defined hash
  functions will result in new databases that use the default hash
  function.  Although using the default hash function may not be optimal
  for the new database, it will continue to work correctly.

Have anyone noticed whether or not such backed-up databases are slower
than "original" databases?  Since slapd precalculates hashes and uses a
no-op hash function in back-bdb/dbcache.c, I suppose that means all data
are hashed twice - once by slapd and once by Sleepycat.

The manpage continues:

  Dumping and reloading Btree databases that use user-defined prefix or
  comparison functions will result in new databases that use the default
  prefix and comparison functions.  In this case, it is quite likely
  that the database will be damaged beyond repair permitting neither
  record storage or retrieval.

Since db_dump is recommended, I take it back-bdb does not use Btree
databases?

-- 
Hallvard