Re: Have ext3 on SanDisk CF but can't disable write-back caching as kernel instructs

From: Dan Harkless (usenet_at_harkless.org)
Date: 07/18/03 

Date: 17 Jul 2003 20:30:25 -0700

Michael Schnell <mschnell@lumino.de> wrote in message
news:<3F166C0A.76DAD013@lumino.de>:
> > We're going to do some timing tests to make sure the sync can finish
> > during our capacitor power time window under typical "write loads" for
> > our application.
>
> How will you determine that the card is ready with the write back ? I
> suppose they use a cache and do internal work long after the actual IDE
> request is done.

Urk. Good point. And that finally brings us back to my original
question about 'hdparm -W0' not working on the CF disk.

Well, /proc/ide/hdc/cache reports "1", so I guess when doing the
timing tests as long as there's more than 1K of outstanding writes,
we'll know that the sync() isn't just returning after doing zero work.

I guess there'll always be a margin of error of <time it takes for 1K
to be written out of CF write cache to actual CF storage>. 

--
Dan Harkless
usenet@harkless.org
http://harkless.org/dan/

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