Thread: Shouldn't the system detect and reallocate bad sectors in flash memory?
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malfunctioning is offline malfunctioning
2014-10-24 , 18:36
Posts: 330 | Thanked: 556 times | Joined on Oct 2012
#13
Originally Posted by javispedro View Post
Yes, every N900 has bad blocks from the factory. However, as said, the eMMC is the one doing wear level and error correction. If you're seeing "bad blocks" at the filesystem level, something is broken, period. No one's N900 is "silently corrupting" data every so often.

You're seeing what looks very much like random read errors, which points to cables or contact points or sth else like that. The kernel message log (ie dmesg) will have additional info.
I think you are absolutely right, thank you for pointing this out.

My N900 has been so reliable for the past 3 years, that I wasn't expecting this sort of problem. This is my main N900, in constant use. Only flashed a couple of times.

I did drop the phone twice to concrete. The Otterbox case protected the phone to the point that it looks as new externally, but it is obvious that the possibility of microfracture somewhere in the eMMC chip is real.

I ran badblocks on my 8GB MyDocs FAT32 partition, and I got 3474 bad blocks (3.5MB out of the 8GB). The pattern exhibits clusters of bad blocks (clusters of a few hundred bad blocks at a time, mainly, so flash wear doesn't fit the pattern.

Also, I ran the same test on another N900's 27GB MyDocs partition, and I got 0 bad blocks. This one is running CSSU Thumb and mildly overclocked (500Mhz min / 805Mhz max).

For now, what I will do is attempt to get around this issue by manually running fsck.ext3 and tagging bad blocks into the filesystem table. I will monitor the progression of bad blocks as well, to see if new ones develop (which I expect to be the case).

Thank you again for clarifying that in a healthy N900 the eMMC chip itself manages bad blocks transparently to the filesystem.