How to temporarily speed up a JFS2 filesystem
UrbanBiel 0600017E5Q Visits (3110)
Some products apparently have to install dozens of thousands of files to look mature. If you install them on localy attached disks, installation and possibly deinstallation takes very long time. There is a way to speed it up significanly.
A little mental exercise: How many IO operations are necessary to create a file in a directory? Let's count:
This is just to create a file, not to write any data into it. On one hand nearly every write is preceded by a read (to find out where to write), but on the other hand there is some caching and (let's believe) some optimization on AIX, thus exact number of IOs is really hard to tell.
You probably guessed it already: Try to switch off the filesystem journal and see what happens. Indeed, you can use this approach for different scenarios but keep in mind, that during the time journal is turned off, your filesystem is much more vulnerable to errors if AIX crashes or storage goes down.
To mount a filesystem with journaling switched off, run
mount -o log=NULL /mountpoint
Yes, it's ~500 seconds vs. 4 seconds. Repeatedly.
There is also a few other good articles on this topic, here is one from Anthony English.