Re: AW: multiple slapd instances on one server

[Daniel Tiefnig <openldap@qmail.infonova.at>]

"Mark Adamson" <adamson@andrew.cmu.edu> wrote...
> > we're planning to run multiple (4 in this case) slapd instances on a
> > single server to increase performance.
>
> 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.

yes. that are problems i worried about..

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

that's what we're planning to do.

> and have 4 slapd.conf files, and let slurpd replicate to the 3 RO copies.

actually we have two servers, one acting as master, and one which should run
4 slaves now. (ok, even more actually there is a third ldap server at the
moment, acting as a slave, but don't mind..) we modified slapd to be able to
bind to a specific interface (IP) and added three more IP adresses which
will then be contacted by our L4 switch.

> 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

the db files are located on a storage server, shouldn't be a problem.

> BER encoding and decoding of all the data, but also for having another
> critical process running.

we're replicating anyway, and i don't worry about slurpd. worked fine all
the time so far..

thx for your reply(ies),
daniel