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slow batch MODIFYs


I'm trying to track down why our OpenLDAP is pretty slow when running
a batch of modify operations.

here's the facts:

* Linux 2.4.7, reiserfs, 4 GB RAM
* openldap REL_ENG_2
* dbnosync is ON, dbcachesize 100 MB per index.
* Sleepycat 3.2.9 BTREE.
* I'm doing MODs of 5-6 attributes per record out of which 2 are indexed
* slapd does 1-2 records per second
* this causes about 200-300 disk write I/O operations per second (!!)
  I can track this on our RAID controller. This is about the maximum the
  disk can do, so this is likely to be the bottleneck. This is all
  WRITE. Few to no READs.

I would expect a MODIFY to cause 2 or 3 write operations - not 200 or
300. Also, shouldn't most of these writes go to RAM with a dbcachesize
that high ?

Can anyone with more insight into database internals enlighten me why this is happening and what to do against it.

Thanks alot,