Subject: RFC: community requirements for a flash filesystem
To: None <firstname.lastname@example.org>
From: David Young <email@example.com>
Date: 03/19/2006 19:15:17
I am seeking the NetBSD community's requirements and recommendations
for a flash filesystem that is suitable for embedded systems.
To start, let me state some bare minimum requirements:
* Survives abrupt power loss: data in buffers may be lost,
but the filesystem is consistent following power loss---no
fsck is required.
* Wear-levelling: on flash parts that require it, avoids R/M/W on
"chunks" smaller than the media's sector size, avoids
concentrating writes on a few physical sectors, "retires"
worn-out sectors. Avoids counteracting wear-levelling by
firmware/hardware on parts that provide it (e.g., CompactFlash),
as a run-time option.
* Supports "typical" embedded uses: loading programs,
(re-)writing configuration files, writing logs. Temporary files
are expected to be on a tmpfs.
Is either FFS or LFS a foundation to build a flash filesystem on, or
should NetBSD build its flash filesystem from scratch? Help me get a
sense of the community on the question.
Can a flash filesystem that meets the needs of 99% of embedded
applications, also satisfy 95% of NetBSD server applications?
How many developer-months away is a usable flash filesystem for NetBSD?
David Young OJC Technologies
firstname.lastname@example.org Urbana, IL * (217) 278-3933