Frequent Writes to NAND flash with UBIFS in sychronous mode

[Artem Bityutskiy]

On Thu, 2012-11-08 at 09:51 +0000, Joe wrote:
> Hi,
>  I have the following observation when UBIFS is mounted as synchronous fs. (-o
> sync option from bootargs). 
> 
>  1. For every file read, there are writes  to nand flash. 

I do not believe it is UBIFS's fault. May be shell history?

>  2. For the execution of every command, there are writes to nand flash. 
>  For ex. On execution of any command, say 'cd' or 'ls' i observe quiet a few
> writes happening to NAND flash.

Also I do not believe it is UBIFS's fault.

> 
> What could be the reason for this behaviour? Any other option to bring down the
> amount of writes but by retaining the synchronous behaviour? 

This is your environment most probably.

> With sync option enabled, we expect Flash writes to happen more frequently ,
> how-ever we do not want  writes to happen with the execution of every command. 

Sure, explore who does the writes and why. E.g., enabe the "general" extra
messages - this should print PIDs and file-names for all I/O. See

http://www.linux-mtd.infradead.org/faq/ubifs.html#L_how_debug
 
> This observation holds true for linux 2.6.28, 2.6.35 & 3.4.10 linux kernel
> versions. 

-- 
Best Regards,
Artem Bityutskiy

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