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Re: How much time is needed to snyc?

On Fri, 5 Jan 2001, Gregory Schallert wrote:

> On my embedded system I would like to sync on powerdown.  I'm sure jffs
> does this under normal conditions, but I am designing a small supply
> that will keep up the power in case of a power failure for enough time
> to shutdown nicely.

JFFS currently runs with O_SYNC semantics at all times - the data are
flushed to the medium before the write() call returns.

> My worse case is that I would have to write a 4Meg Ramdisk back to the
> JFFS/MTD Flash chip.

I'm not sure what you mean here. Do you mean you load a ramdisk off the
flash on boot, and write the modified copy of the ramdisk in its entirety
out to the flash on shutdown? Why?

> I can look at the specs of the Flash chip and get the worse case for
> the write, but I was wondering how much additional time is the worse
> case would JFFS take to sync?

Zero. When we start to implement write-behind, that'll change. But we'll
make sure we have a sync mount option.


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