Finding a suitable filesystem

[Joseph C. Lininger]

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> Out of interest why would a journaling FS wear out the drive quicker?
> I haven't seen comment of this in my searches.

The reason has to do with the way journaling filesystems work. The
summary is this. Journaling filesystems contain a log or journal of
changes they are going to make to the filesystem. If you create a new
file, for example, the changes to the filesystem necessary to create the
file are recorded in the journal. Then the changes are made to the
actual filesystem. What this does is to provide filesystem consistancy
in the event your system crashes in the middle of a change to the
filesystem. That way you don't have to do an extensive check of the
filesystem to bring it to a consistant state. Replaying the journal
takes anywhere from a few seconds to a few minutes, instead of the
filesystem check taking anywhere from a few minutes to a few hours. I
should point out that most journaling filesystems don't journal all data
you write. They only journal changes to the metadata (structures used to
keep track of files in the filesystem). This is done for performance
reasons.

Now the reason why journaling filesystems ware out your drive faster is
that the filesystem typically allocates a specific portion for the
journal, then continuously writes to it every time a change is made to
the filesystem. Most flash drives have a chip which is rated for a
maximum of about 100000 writes. The
constant writing and rewriting of the portion allocated for the journal
causes the chip to ware out rather quickly. A write to the journal is
generated for, well, just about everything on a journaling filesystem
mounted read-write. The following are examples:

* File creation and removal
* Editing a file
* Any access of a file (if noatime option is not in use)
* Creation and removal of directories

Hope this helps.

Joe
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