Re: Which file system for Emdebian Grip: JFFS2 / YAFFS2
+++ Bjørn Forsman [2011-03-03 12:56 +0100]:
> Hi,
>
> 2011/3/3 Jean-Michel Pouré - GOOZE <jmpoure@gooze.eu>:
> > Hello,
> >
> > Which file system would you recommend for an Emdebian grib filesystem on
> > Compact Flash? I would expect to see JFFS2 / YAFFS2 but it is not
> > available from the Debian installer.
>
> AFAIK, Compact Flash emulates a block device so the pure flash-based
> filesystems like JFFS2 and YAFFS2 doesn't make much sense. I think
> it's better to use one of the non-flash filesystems, e.g. ext2/3/4,
> for Compact Flash.
Correct. CF (or SD or MMC) is a block device interface for 'normal'
disk filesystems (ext2/3/4/btrfs etc). I believe eMMC (which is
soldered-down flash that behaves like an MMC card) also falls into
this class.
On-board flash, or Smartmedia (or xD I think) is raw flash that needs
a flash filesystem JFFS2/YAFFS/UBIFS/(LOGFS)
A long time ago (6 years?) I had very bad experiences with ext3 and CF
(wear-levelling/ad-block management was at the front of the device,
where the FAT goes, not at the end where the ext3 journal goes, so a
few boots could kill the device). Controllers have improved so this is
not a problem anymore, but they are still all designed for FAT and
thus work less well to varying degrees and in varying ways with other
filesystems. Simple-minded filesystems may well work better than
clever ones, depending on the details of their operation.
Wookey
--
Principal hats: Linaro, Emdebian, Wookware, Balloonboard, ARM
http://wookware.org/
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