Oracle Tips by Mike Ault
The ReiserFS 3.6.x (the
version included as part of Linux 2.4) was designed and developed by
Hans Reiser and his team of developers at
The ReiserFS uses a specially optimized b* balanced tree (one per
filesystem) to organize all of its filesystem data. This offers a nice
performance boost, as well as easing artificial restrictions on
filesystem layouts. It's now possible to have a directory that
contains 100,000 other directories, for example. Another benefit of
using a b*tree is that ReiserFS, like most other next-generation
filesystems, dynamically allocates inodes as needed rather than
creating a fixed set of inodes at filesystem creation time. This helps
the filesystem to be more flexible to the various storage requirements
that may be thrown at it, while at the same time allowing for some
ReiserFS also has a host
of features aimed specifically at improving small file performance.
Unlike ext2, ReiserFS doesn't allocate storage space in fixed one k or
four k blocks. Instead, it can allocate the exact size it needs. And
ReiserFS also includes some special optimizations centered around
tails, a name for files and end portions of files that are smaller
than a filesystem block. In order to increase performance, ReiserFS is
able to store files inside the b*tree leaf nodes themselves, rather
than storing the data somewhere else on the disk and pointing to it.
This does two things.
First, it dramatically increases small file performance. Since the
file data and the stat_data (inode) information are stored right next
to each other, they can normally be read with a single disk IO
operation. Second, ReiserFS is able to pack the tails together, saving
a lot of space. In fact, a ReiserFS filesystem with tail packing
enabled (the default) can store six percent more data than the
equivalent ext2 filesystem, which is amazing in itself.
However, tail packing
does cause a slight performance hit since it forces ReiserFS to repack
data as files are modified. For this reason, ReiserFS tail packing can
be turned off, allowing the administrator to choose between good speed
and space efficiency, or opt for even more speed at the cost of some
Of course we also have
many other filesystems such as those from Veritas, Polyserver and
other specialized systems.
Generally Oracle prefers
filesystems that don’t do logging or journaling for filesystems that
contain datafiles so if you use EXT2, EXT3 or reiserFS you need to
mount them with the journaling or logging off. If RAW filesystems are
used you avoid some overhead but usually can only obtain a 2-5 percent
performance increase over modern optimized filesystems.
SEE CODE DEPOT FOR FULL SCRIPTS
For more information on this topic, I recommend Don
Burleson's latest book "Oracle
Tuning: The Definitive Reference".
You can buy it direct from the publisher for 50%-off and get
instant access to the code depot of Oracle tuning scripts:
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