Axis log based flash file system

[Finn Hakansson]

On Tue, 28 Mar 2000, ±Ç¼®±Ù wrote:

> Hi, all
> In my thought, JFFS work of Axis was good for frequent log/delete
> applications
> like network printer or image server for web cam. But not good for general
> file system.

That is correct. JFFS was designed with small flash devices in
mind. It would of course be possible to use it with other devices
though.


> Because, in JFFS, wear-leveling is only meaningful when old file is deleted
> and
> new file is created frequently (just like printer server).  maybe that's why
> they called it implicite.

Well, since the file system is organized as a circular buffer
that is rotated around the flash, the different parts of the
flash device is used equally much. It could be seen as an
implicite effect.


> (wear leveling could be occur but not sure.)
> In situation where 80% of flash is steady (kernel + basic utils nerver
> deleted) then only 20 % of
> flash could be used in rotation. And if 20 % of flash could be fragmented
> stopping rotation.  Maybe my understanding about JFFS (i just followd full
> source
> once)  would be poor. and I need more notes from axis people.
> Thansk.

In our products, we have the kernel and different programs on other
partitions with other file systems (i.e. ROMFS). We have a partition
with JFFS which is used for configuration files that the user can
modify (i.e. /etc). To that partition, a user can upload his own files.


/Finn



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