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-   Maemo 5 / Fremantle (https://talk.maemo.org/forumdisplay.php?f=40)
-   -   If flash memory doesnt last very long - how long will my n900? (https://talk.maemo.org/showthread.php?t=48192)

qwazix 2010-03-24 14:40
Re: If flash memory doesnt last very long - how long will my n900?
 
what about the rootfs? That's being read and written all the time. And the swap? A different partition doesn't mean specific blocks? SD cards that hold photos never go near the number of writes an OS does when its running.
________
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TA-t3 2010-03-24 14:51
Re: If flash memory doesnt last very long - how long will my n900?
 
Quote:
Originally Posted by extent (Post 580335)
if old blocks for data fail, and the phone can detect them and write to a different block instead (would i need to install an app for making sure bad blocks are never written to again?) then the phone should last a fair while, especially when theres this much space available... thanks
Wear-leveling on SD cards isn't handled by the device, it's a built-in feature of SD (and MMC) cards.

TA-t3 2010-03-24 14:58
Re: If flash memory doesnt last very long - how long will my n900?
 
Quote:
Originally Posted by cashclientel (Post 580386)
@TA-t3 - Don't be so sure that the device does this. My Olympus camera (1 yr old) always fills 'from the bottom up' and over writes old blocks as soon as they are free. I'd expect the N900 not to do this as it's should really be more intelligent, but I'm sure.
Is that SD? Sure it isn't XD? In any case, how would you know if the blocks are overwritten (not moved), it's not something that's visible on the operating system layer. And finally, the SD specification includes built-in wear leveling.

http://en.wikipedia.org/wiki/Flash_memory#Memory_wear

TA-t3 2010-03-24 14:59
Re: If flash memory doesnt last very long - how long will my n900?
 
Quote:
Originally Posted by qwazix (Post 580401)
what about the rootfs? That's being read and written all the time. And the swap? A different partition doesn't mean specific blocks? SD cards that hold photos never go near the number of writes an OS does when its running.
That's the built-in flash, not an SD card. Different rules apply. The eMMC is a different story again.

cashclientel 2010-03-24 15:06
Re: If flash memory doesnt last very long - how long will my n900?
 
@TA-t3 - It's SD and I'm sure of the behaviour as I've performed data recovery on the space and tested it.

You've misquoted Wikipedia there as well (outrageous behavior)
Quote:
effect is partially offset in some chip firmware or file system drivers by counting the writes and dynamically remapping blocks in order to spread write operations between sectors; this technique is called wear levelling
anyway, this is moot until someone tests the N900.

ioan 2010-03-24 15:07
Re: If flash memory doesnt last very long - how long will my n900?
 
Quote:
Originally Posted by extent (Post 580245)
doesnt reading from flash memory age it as much as any writing? i always thought it did
That's RAM. A reading from RAM refreshes the info (the state of each cell) just like a write.

extent 2010-03-24 16:49
Re: If flash memory doesnt last very long - how long will my n900?
 
yeah, i just thought it might have been the same with flash, I guess not! :) thanks

cazzajay 2010-03-24 17:42
Re: If flash memory doesnt last very long - how long will my n900?
 
i wouldnt worry, im using a 64MB CompactFlash card i got in 2001 to transport files from OSX to Windows in bootcamp (using a card reader) and its never let me down.....so far(?)

Aydan 2010-03-24 17:54
Re: If flash memory doesnt last very long - how long will my n900?
 
Quote:
Originally Posted by ioan (Post 580445)
That's RAM. A reading from RAM refreshes the info (the state of each cell) just like a write.
What you mean is D(ynamic)-RAM since flash is also a type of Random Access Memory. The N900 has only RAM type memory.
I also suspect that the root partition might be a different flash technology with smaller memory blocks or longer lifecycle.

wmarone 2010-03-24 18:10
Re: If flash memory doesnt last very long - how long will my n900?
 
Quote:
Originally Posted by qwazix (Post 580401)
what about the rootfs?
The rootfs is managed by UBIFS, which does wear levelling across the entire 256MB.

Quote:
That's being read and written all the time.
Not as much as you might think. Most of the files on the rootfs are extremely static.


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