Load-Average with different backends on different filesystems

[Markus Schabel <markus.schabel@tgm.ac.at>]

Hello!

After having switched our LDAP servers from ldbm to bdb we encountered
some interesting problems:

On one server the load average went up to somewhere between 30 and 50,
but all other machines (same config, similar amount of LDAP access and
searches) stayed around 0. The only difference between the machines is
the filesystem: with xfs, ext2 and ext3 there are no problems, but with
reiserfs there is no productive use possible (at least with default
configuration).

After googling a bit I found out that it is known that the system does
not perform fast on journaling filesystems and bdb with inproper cache
settings, but since most accessing operations (max. one write per min)
are read that should be no problem (especially if it performs well with
other filesystems).

After looking a while into Doc and FAQ I didn't find anything that
states that there may be some filesystems that should not be used with
bdb (but there are some postings in the archive), so maybe this info
should be included somewhere.

After switching back to ldbm on this server all things are fine again.
And hopefully I'll find the time to migrate the machine to xfs...

best regards
Markus
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