Re: [MiNT] ext3/ext4

[Eero Tamminen <oak@helsinkinet.fi>]

Hi,

On Monday 10 May 2010, Stefan Niestegge wrote:
> > AFAIK it keeps a journal and so if there is a crash and the system
> > has to reboot it doesn't have to check the filesystem. Otherwise
> > it is the same as ext2.
> >
> > http://en.wikipedia.org/wiki/Ext3
> >
> > I think Ubuntu uses ext3 or possibly ext4 by now

Ext4.  In most things it's faster than Ext3, but it has some design
issues which require workarounds in programs which make it slower
than Ext3.

(google for "ext4 atomic renames" for the issue these programs try
to avoid and how ext4 maintainer thinks that should be done.)


> Exactly, and with help of that journal, filesystem errors (that in fact
> occur with ext3 as well) can be more safe recovered.
>
> I just happen to exprience a FS check. Some stuff was bound to
> lost&found during that,
> now my MiNT moans about some folders in /etv/var and similar not found.
>
> I will have to reinstall. Ext3 most probably would have saved me from
> that.
>
> So, if someone thinks, ext3 could be possible to port for our MiNT
> system, i vote for it.

They both journal the disk metadata, not the file contents.

I.e. your file system can be fine after crash, but your file contents
may still be messed if a file write was interrupted.

Journaling also slows things down as (meta) data is written twice, first to
the journal, then to the disk.  I'm waiting for log based file systems,
they're the next big thing after journaling file systems.  :-)


	- Eero