[Nottingham] USB flashing your distro?
penfoldq at penfoldq.co.uk
Wed Apr 16 16:17:51 BST 2008
On Wed, Apr 16, 2008 at 01:59:25PM +0000, ForkBombFluf wrote:
> On Wed, 16 Apr 2008, Andy Smith wrote:
> >True, but with the very low cost of these products I am not
> >surprised they aren't willing to state anything complicated like
> >that. Crucial offer a lifetime warranty. Kingston offer a lifetime
> >warranty. SanDisk offer a 5 year warranty.
> >Kingston CF media is rated for 10,000 write cycles per sector with
> >wear levelling - they state that this will last for 27 years of
> >rewriting the entire media once per day.
> 365 * 24 = 8760 hours in a year, so if it was to rewrite the whole drive
> once an hour it's possible it might last a little
> over a year on average, assuming the more constant read/write cycle (as
> opposed to 27 years) doesn't make it wear
> out quicker .
> Can't argue with the price of course, that's certainly where they win
> out... But how to get a bit more fault tolerance?
As Cam has said, in embedded environments, regular incremental writing
(appending to log files) causes these blighters to wear out really
quickly. With a bug that caused writes every 5 milliseconds, we wore
these disks out in a few hours. Sent them back to the manufacturer and
they said the disks were worn out. Plus undocumented firmware bugs in
the CompactFlash controllers that you only get told about once you've
fallen foul of them and all in all, CompactFlash was a pain to integrate
into our embedded systems. Many of us would have preferred to stick with
discrete flash devices that we can control the writes to more
explicitly. Hey ho.
But as has been said many times already on this thread, you cannot
compete on price and these are only so cheap because the quality control
is lax enough to allow very high yields. Some devices may last forever
you just cannot tell. We had a situation where one supplier said they
would replace faulty disks they had sent us but we found out that they
had shipped them knowing they were faulty in the hope we wouldn't notice
the firmware bug they knew existed. We can only assume they resold the
returns to another consumer who wouldn't notice.
The solid state disk in the Eee concerns me somewhat for just that
reason but again, you cannot make it better without making it _MUCH_
Just my experience of working on device drivers for CompactFlash disks
in an embedded environment. USB Flash is similar, its the only way they
can keep costs so low.
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