[ILUG] Linux Myths. The truth can be told!

[Vincent Cunniffe]

ilug-admin at linux.ie wrote:
> 
> Ronny Bangsund wrote:
> 
> > Note how they mentioned the lack of a journaling filesystem
> > in Linux, but evaded mentioning what sorry excuse NT has for
> > one. It's still NTFS (or whatever), isn't it?
> 
> Just a quick question from the ignorant ..
> What is the difference between a Journaling & non-journaling FS

A journalling fs keeps a little log of what it's planning on doing,
and when it's done, it wipes the log.

If the system crashes in the middle of a disk operation, the fs can
quickly look up the journal, find out what was supposed to be done,
and complete the operation. This means that it can be sure that no
damage was done to the fs during the crash, or if it was, it'll
know precisely what operation was in progress and thus precicely
what went wrong.

This allows a system to avoid lengthy fscks on reboot (it can take
*hours* for a hefty 100G GB+ fs to finish fscking), and means that
the server can come back up instantly.

Linux has 3 JFS's in the pipeline at the moment, one of them being
SGI's commercial-grade, heavily proven one which they made open 
source a few months back.

Vin