How reliable is jffs2 really (denx cvs devel kernel)?
Wolfgang Denk
wd at denx.de
Wed Jul 20 18:37:32 EST 2005
In message <200507200830.27141.david.jander at protonic.nl> you wrote:
>
> I already thought it might be a good idea to subscribe to that list.
> Any hint about how I can figure out exactly which version of MTD code I have?
I already answered this in my previous message: it's a snapshot from
MTD CVS of March 13, 2005, backported to the 2.4 kernel.
In general, you can find this type of information when checking the
CVS history. That's why we run a CVS server and not only provide
tarballs.
> The version of linuxppc_2_4_devel I have is about 2 months old, do I have to
> expect important changes concerning MTD since then?
More changes have been made since, of course, but I'm not aware of
anything that might be relevant to your problem.
> need to log data into flash. Right now I use an oversized jffs2 partition,
> log via syslogd and logrotate on size. I am getting the impression that this
This is about the worst case use for JFFS2 - always appending small
chunks (sinlge lines of text) to an ever growing file is exactly what
the filesystem was NOT designed for.
> is not workable for mission critical things. At least not with the kernel and
> MTD code I have. Others must have the same problem, so here's my question:
> Which way to do such a thing? Write my own filesystem?
No. Don't reinvent the wheel. Use a buffer are with unlimited write
cycles (like SRAM or FRAM), or even a reserved area of your system
RAM, and use pramfs on it. If you're using U-Boot, you can even
arrange that such a file system survives warm boots. Then establish a
policy for writing the data from this buffer area to flash (probably
still using JFFS2) at a much lower rate. Avoid append mode. Try to
write files in a single operation. etc.
Best regards,
Wolfgang Denk
--
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"Summit meetings tend to be like panda matings. The expectations are
always high, and the results usually disappointing." - Robert Orben
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