Subject: Re: MTD devices in NetBSD
To: David Brownlee <>
From: Charles M. Hannum <mycroft@MIT.EDU>
List: tech-kern
Date: 03/23/2006 12:40:29
On Wed, Mar 22, 2006 at 06:45:08PM +0000, David Brownlee wrote:
> 	From a hardware perspective you should be able to perform
> 	sub-block writes down to the word level. A perfect example
> 	of that usage would be a an app performing synchronous
> 	appending writes to a logfile. Providing you are not
> 	_clearing_ any bit in the current block you can just 'write
> 	over' the current values (assuming standard flash).

Unfortunately, current file systems like FFS can't do this, because they
zero all the unused data in a block, and rewrite it every time.  This is
a good example of why a flash-aware file system is important -- you can
save a lot of wear, and gain a lot performance here.