[CALUG] Can Media cards have bad blocks?

[Bryan J Smith]

It's not similar to disk technology.  In disk technology, sector
write failures are in excess of 10**13, although it does not
mean the sector has failed.  In NAND technology, block failures
are around 10**3, and a completely removed once a threshhold
is reached.  As such, block rotation is _mandatory_ with NAND,
wholly unlike disk technology.  In reliable design, this is done by the
OS and filesystem (e.g., Linux JFFS2).  But Windows doesn't
offer such, so auto-rotated logic is provided by commodity
devices.

Also, _never_ do a dd or complete block wipe.  You _destroy_
the longevity of the device.  Again, most people shouldn't assume
anything about commodity NAND, because it's wholly unlike
anything they've ever dealt with. ;)

--  
Bryan J Smith - mailto:b.j.smith at ieee.org  
http://www.linkedin.com/in/bjsmith
Sent via BlackBerry from T-Mobile  
    

-----Original Message-----
From: Rajiv Gunja <opn.src.rocks at gmail.com>
Date: Fri, 9 Apr 2010 19:41:01 
To: <b.j.smith at ieee.org>
Cc: James Ewing Cottrell 3rd<JECottrell3 at comcast.net>; <calug-bounces at unknownlamer.org>; CALUG<calug at unknownlamer.org>
Subject: Re: [CALUG] Can Media cards have bad blocks?

After confirming that there could be bad blocks, I erased all data from my 8
GB Micro-SD card and my mobile (using BlackBerry - wipe-device).
Interestingly, I have no issues now on the memory card. Wonder if those bad
blocks were remapped similar to the HDD remapping technology.

I am waiting for a good deal so I can buy a 16GB MicroSD card to replace it.

-GGR

--
Rajiv G Gunja
Blog: http://ossrocks.blogspot.com


On 9 April 2010 19:30, Bryan J Smith <b.j.smith at ieee.org> wrote:

> All commodity NAND blocks have bad cells from virtually day 1.
> Within 1,000 writes, they will be unreliable.  These are the reality
> of the technology today.  They are also normally very slow at
> writes, but techniques are used to sychronize commits in the
> circuits.
> Access times are much better than disk, but still poor next
> to actual DRAM (let alone SRAM).  NAND != RAM, no matter how
> much people assume otherwise.
>
> --
> Bryan J Smith - mailto:b.j.smith at ieee.org
> http://www.linkedin.com/in/bjsmith
> Sent via BlackBerry from T-Mobile
>
>
> -----Original Message-----
> From: James Ewing Cottrell 3rd <JECottrell3 at Comcast.NET>
> Date: Fri, 09 Apr 2010 18:42:04
> To: Rajiv Gunja<opn.src.rocks at gmail.com>
> Cc: CALUG<calug at unknownlamer.org>
> Subject: Re: [CALUG] Can Media cards have bad blocks?
>
> If you asked me 8 days ago I would have said...
>
> No. Flash drive always record all data accurately.
>
> But the other 364 days a years....
>
> If a device can have Good Blocks, it can have Bad Blocks.
>
> JIM
>
> Rajiv Gunja wrote:
> > Hello,
> > I have been using my Mobile to listen to Music and Audio books rather
> > than carry around both my Mobile and iPod. The other advantage being, I
> > have a stereo bluetooth headset for my Mobile.
> >
> > On the media card 8GB MicroSD, There are folders created by my
> > BlackBerry. I have created couple of folders on them too, within the
> > directories it has created.
> >
> > Under Documents, I have created Audiobooks and eBooks. For some reason,
> > if I copy my MP3s to "Music" folder created by the BB OS, BB hangs and
> > becomes very slow and I have remove the SD card to make it respond.
> > Whereas if I copy those same MP3 files to "Audiobook" directory, it
> > works fine and plays fine too.
> >
> > Is this because there are bad block or whatever is holding the
> > information? Is it time to buy another card?
> >
> > -GGR
> >
> >
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
> > CALUG mailing list
> > CALUG at unknownlamer.org
> > http://lists.unknownlamer.org/listinfo/calug
> >
> >
> > ------------------------------------------------------------------------
> >
> >
> > No virus found in this incoming message.
> > Checked by AVG - www.avg.com
> > Version: 9.0.791 / Virus Database: 271.1.1/2775 - Release Date: 03/28/10
> 02:32:00
> >
>
> _______________________________________________
> CALUG mailing list
> CALUG at unknownlamer.org
> http://lists.unknownlamer.org/listinfo/calug
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.unknownlamer.org/pipermail/calug/attachments/20100410/44deb53c/attachment.htm