Subject: RE: NetBSD File Systems
To: None <firstname.lastname@example.org>
From: amaya <email@example.com>
Date: 03/05/2001 22:30:16
Actually, some flash file systems can be used for limited R/W use
without much special concern. A good NAND flash based system will have a
basic erase cycle life of ~1e6 erases. When you combine this with ECC, bad
block retirement (they get a tiny gold watch) and wear leveling, lifetime
for _limited write rates_ is quite good.
For example, in a little system I've had running for a year now,
the flash is 16M with 12M used by NetBSD and 4M free. My write rate is
quite slow (I've turned off most logging) maybe 50K bytes per minute at
the worst. So if I take 50K per minute/24 hours a day, writing and
rewriting that 4M byte area, I will have about 152 years before I get to
1E6 erases on all the blocks in the 4M area...
The thing that is missing for low cost systems where directly
addresed flash is used as both as boot ROM and file system, is a flash
file driver that does the wear leveling, bad block retirement, and ECC. I
guess there is source for a FFS available for Linux (from Axis) but I have
no idea how good it is...