Re: AW: multiple slapd instances on one server

[Mark Adamson <adamson@andrew.cmu.edu>]

I can think of two problems that you might see. First, the database
routines probably won't let you open the db files from multiple processes.
BDB does locking within the db file header, so other processes trying to
open it, especially with one writer and multiple readers, will fail.

The other problem is if the writer process writes to cached entries in
memory and doesn't flush to the disk right away, you may get old data from
reading from the RO servers.


What you may consider doing is making 4 copies of the db in separate
directories

/usr/openldap/db.rw
/usr/openldap/db.ro.1
/usr/openldap/db.ro.2
/usr/openldap/db.ro.3

and have 4 slapd.conf files, and let slurpd replicate to the 3 RO copies.
You could put the RO db files on their own disks to overcome disk head
seek times.  However, you take a loss on running slurpd not only for the
BER encoding and decoding of all the data, but also for having another
critical process running.

-Mark Adamson
 Carnegie Mellon


> we're planning to run multiple (4 in this case) slapd instances on a
> single server to increase performance.