David Woodhouse dwmw2 at infradead.org
Tue Jul 25 09:19:44 EDT 2000

bjornw at axis.com said:
>  It usually takes about 1-2 seconds to erase a sector, so if you
> really need to erase the entire 16 mb flash during GC, that's 250
> sectors times 2 seconds, about 8 minutes. Mileage may vary depending
> on flash manufacturer - I've never used 16 mbyte flashes in anything..

On these chips, erases only take a second. At the time, it was also 128
microseconds per _word_ write. So although a complete erase only takes 128
seconds, writing the whole device was more like 20 minutes.

Even so, it should be far less than the 90 minutes that I observed. Is it
possible that the GC was compacting the data on the flash repeatedly, before
it had completed removing all the files? The command I was running was:
 rm -r /mnt/usr

If it removed a couple of MB, then garbage collected, then removed another 
couple of MB, then would it have ended up moving the same data twice?


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