Re: Swap on flash SSDs

[Ingo Molnar <mingo@elte.hu>]

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Fri, 18 Dec 2009, Ingo Molnar wrote:
> > 
> > And even when a cell does go bad and all the spares are gone, the failure 
> > mode is not catastrophic like with a hard disk, but that particular cell 
> > goes read-only and you can still recover the info and use the remaining 
> > cells.
> 
> Maybe. The real issue is the flash firmware. You want to bet it hasn't been 
> tested very well against wear-related failures in real life?

I certainly dont want to bet anything on technology that is just a few years 
old :-) I have an SSD, and i keep backups.

( Okay, i have to admit that i have a weakness for certain types of unproven 
  technology, such as toy kernels that are just a hobby ;-)

> Once the flash firmware gets confused due to some bug, the end result is 
> usually a totally dead device.
> 
> So failure modes can easily be pretty damn catastrophic. Not that that is in 
> any way specific to flash (the failures I've seen on rotational disks have 
> been generally catastrophic too - people who malign flashes for some reason 
> don't seem to admit that rotational media tends to have all the same 
> problems and then some).

There's also electronics failure that could occur. Plus physical damage.

But at least data recovery does not need a clean room ;-) [ If the cells are 
still undamaged, if it wasnt a lightning strike, an earthquake or a two year 
old that damaged them then an identical model can be used for recovery. ]

( If the data matters. If it doesnt then nobody will care about anything but
  everyday usability, a lifetime of at least a few months, plus price,
  performance/latency and maybe shock resistence. )

	Ingo

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