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10/08/2009 12:35:05 PM · #1 |
OK, so I may have totally misunderstood what wear levelling is, but bear with me if I have:
As far as I understand it, wear leveling on flash media ensures that fresh data is written to the next oldest used sectors (not the portions that have most recently been used).
Why doesn't it? Every time I do photo recovery, the new photos are right at the beginning & the way old ones are still there...
Anyone care to enlighten me? (Google wasn't much help)
Thanks
Message edited by author 2009-10-08 12:36:10. |
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10/08/2009 01:47:13 PM · #2 |
It will appear the same to you. The difference is in the addressed sectors that the computer is utilizing. By design, this is something you will never see.
Or, am I not understanding your question?
Message edited by author 2009-10-08 13:48:00. |
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10/08/2009 02:43:02 PM · #3 |
| Yes, as Yo_Spiff said, the controller on the card performs the leveling function. When you read the card, you are only seeing what the controller reports, not the actual structure of the physical data. |
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10/08/2009 02:49:56 PM · #4 |
Thanks so much for your reply. Tell me more if you can.
The way I imagine it (& what doesn't make sense to me) is in the following two scenarios:
1) Say I write a card 1/4 full with a photo session
2) I re-format it
3) and again write the card 1/4 full
4) then I would imagine the first session to be totally recoverable in some way (at least on a software level, it isn't)
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1) Say I fill a card to capacity
2) Then I re-use it to 1/2 capacity several times, re-formatting it inbetween
3) I would expect the first filled session to become unrecoverable if those older sectors are indeed being re-written. And yet they seem totally recoverable till the media is filled again.
Am I missing something?
Thanks.
Message edited by author 2009-10-08 14:59:17. |
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10/08/2009 03:38:21 PM · #5 |
It would be recoverable, except that the sectors are being remapped transparently. I'm not sure if recovery software would get past that or not.
Found this article from Corsair memory that explains wear leveling (PDF)
Message edited by author 2009-10-08 15:41:38. |
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10/08/2009 03:57:16 PM · #6 |
| The first scenario will result in some potentially recoverable files, however there will be files that get partially or fully over-written. Think of wear leveling as a random process. Even though each block of writes takes up much less than half the available space, there is still a very high chance that some of the written areas will overlap. |
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10/08/2009 04:46:32 PM · #7 |
Thanks for the link & replies. I'll try to wrap my head around it over the weekend.
Message edited by author 2009-10-08 16:46:44. |
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