You're better off with ext2 (or raw partitions if you're feeling
really keen) for a database. As a generalisation, it isn't
a good idea to put databases on a journalling file system for
the following reasons:
(i) The journalling function is redundant as the database
does this anyway. This generates redundant disk
traffic.
(ii) Journalled file system logs are most definitely not
optimised for database access patterns. Databases
generate lots of small writes to big files, which
create disproportionately large log entries with lots
of wasted space (i.e. entire 8k data-base blocks being
written by the db and journalled by the filesystem for
a single-row change). This wastes a large amount of
log space and places a big garbage colleciton burden
on the logs. In some journalling filesystsms such as
LFS the log entries become the new disk blocks for the
filesystem and the old ones are garbage collected -
which would aggravate the external fragmentation of
the database files.
(iii) JFS's don't keep filesystem metadata up-to-date in
realtime - typically there is an asynchronous writer
process that goes through the log and writes out the
changes. On a busy system, this may lead to a lot
of journaled-but-not-written changes which are
inefficient, particularly if there is is significant
locality-of-reference. The logs can also run out of
space if a busy system can't keep up with the garbage
collection.
I've seen an instance of Baan (an also-ran in the ERP racket)
being deployed on an HP-UX box with journalling filesystems.
This had persistent performance and space problems until
someone worked out that they were running the database on a
journalled filesystem. After they reformatted the partitions
as UFS (berkely FFS) the problems went away.
Nigel.
-----Original Message-----
From: Kevin Wilson [mailto:[EMAIL PROTECTED]
Sent: Thursday, 11 September 2003 10:11 a.m.
To: Sapdb General List (E-mail)
Subject: Hard disk lit-up like Christmas tree ???
[System]
SuSE v8.1 w/ using ReiserFS
SAPDB v7.3.0.34
Several sapdb processes are in a Uninterruptible Sleep state and kreiserfsd
keeps popping in every so often. The hard disk is activity is very high and
the database access is slower but still accessible.
Any ideas?
Kevin
"Those who would give up essential liberty to purchase a little temporary
safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759
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