[vox-tech] DVD playback and burning under Debian; IDE DVD+/-RW drive

[Bill Broadley]

On Wed, Dec 03, 2003 at 04:52:29AM -0800, Mark K. Kim wrote:
> I feel pretty comfortable using flash like a hard drive with some
> precautionary measures (with or without jffs).  The number of times you
> can write on flash compared to DVD-RW are a couple orders of magnitude of

Er actually for the 2 types of NAND compact flash that have 10 and 100
times the number of write cycles.

JFF2 can have on the order of 100-1000 times less writes, I forgot
to mention a 3rd difference.  I believe compact flash you can set a zero
to a 1 for "free" but have to clear entire blocks.  So JFFS2 can take
advantage of this to additional reduce the number of writes.

> difference, and comparing them makes it seem like they're on a similar
> level, but they're not (not that you were implying that.)  Just a footnote
> here...  ignore me.

A good point, if you have the 10k write cycle type playing with a large
directory, deleting it, and repopulating it can cause significant wear,
I'm not familiar enough with it to be sure, but I think deleting 4000
files would like cause something on the order of 4000 writes to the
inode for the directory which would be on a couple of blocks.  Although
metadata is stored async so maybe it would be dramatically less then
that.

In any case, with compact flash or CDRW I'd rather use every block of
the filesystem 1,000 (CDRW), 10,000 (SLC NAND), or 100,000 (MLC NAND)
times then just have the worst case being the superblock.

As it turns out there are some issues with JFFS2, currently it's limited
to 4GB, and it's not clear that the datastructures involved would scale
well to filesystems that big.

-- 
Bill Broadley
Mathematics
UC Davis