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Date: Wed, 11 Mar 2015 10:09:11 +0100
From: Richard Weinberger <richard@nod.at>
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Subject: Re: RFC: detect and manage power cut on MLC NAND
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Am 11.03.2015 um 10:05 schrieb Artem Bityutskiy:
> On Wed, 2015-03-11 at 09:57 +0100, Richard Weinberger wrote:
>> Hi!
>>
>> Am 11.03.2015 um 08:20 schrieb Artem Bityutskiy:
>>> On Tue, 2015-03-10 at 13:51 +0100, Richard Weinberger wrote:
>>>>> WDYT about this?
>>>>> If it sounds reasonable is there any suggestion where to place such a code?
>>>>
>>>> Customers often use DYI uninterruptible power supplies using capacitors.
>>>> But managing a power cut is the least problem you have with MLC NAND.
>>>
>>> Why is it the least problem, what is the hardest one? I thought this one
>>> is the hardest.
>>
>> IMHO the hardest ones are the problems we don't know yet as NAND vendors
>> are not really chatty about the MLC constraints.
>> We don't know much about data retention for example. At least we have not
>> much hard facts. Most of our knowledge is hearsay.
> 
> Well, but from the problems we know paired pages seems to be the biggest
> one. E.g., what do we do if VID header gets corrupted because of an
> interrupted write to the page paired with the VID header page? Sounds
> like a hard problem to me.

It is a hard problem. But at least we know about it.

> As for other things, I am not sure. I remember back when I worked for
> Nokia, vendors did tell us everything we needed to know about their
> flash product.
> 

Nokia is/was not really a small player.

Thanks,
//richard