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qwazix is offline qwazix
2010-03-24 , 14:40
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#11
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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Last edited by qwazix; 2011-08-21 at 10:28.
 
TA-t3 is offline TA-t3
2010-03-24 , 14:51
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#12
Originally Posted by extent View Post
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.
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TA-t3 is offline TA-t3
2010-03-24 , 14:58
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#13
Originally Posted by cashclientel View Post
@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
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TA-t3 is offline TA-t3
2010-03-24 , 14:59
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#14
Originally Posted by qwazix View Post
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.
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cashclientel is offline cashclientel
2010-03-24 , 15:06
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#15
@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)
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.
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ioan is offline ioan
2010-03-24 , 15:07
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#16
Originally Posted by extent View Post
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.
Last edited by ioan; 2010-03-24 at 15:10.
 
extent is offline extent
2010-03-24 , 16:49
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#17
yeah, i just thought it might have been the same with flash, I guess not! thanks
 
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cazzajay is offline cazzajay
2010-03-24 , 17:42
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#18
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(?)
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Aydan is offline Aydan
2010-03-24 , 17:54
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#19
Originally Posted by ioan View Post
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.
 

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wmarone is offline wmarone
2010-03-24 , 18:10
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#20
Originally Posted by qwazix View Post
what about the rootfs?
The rootfs is managed by UBIFS, which does wear levelling across the entire 256MB.

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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