[CALUG] Can Media cards have bad blocks?

[Bryan J Smith]

FYI, my warning prior was to those who might try to dd if=/dev/zero
of=device, not that you did such.

The BB command you utilized likely didn't wipe anything but a
key block (like the root of FAT filesystem). All of your data
is likely intact, just removed from any indexing from that key block.
In general many devices can be picky on the format, and are best
formatted by the device before use.  E.g., I only use my SDHC
cards for my dSLR in my one dSLR brand/firmware and don't
rotate them between other devices, other than for Linux
to read. In fact, because Linux can do read-only mounts - while
Windows can't - I always use such after seeing other people
shoot and then Windows corrupt a FAT filesystem SD it didn't
understand proper.

It keeps me from getting burned at least.  Although anytime
you start filling up a NAND device, expect failures shortly afterwards.
It's especially frustrating for users when their device has
reached the point where there are fewer blocks left that
have not reached the failure tolerance than the device reports
for allocation.  I've seen that many times myself, and it's funny
to show the user with a vendor tool (rare these days, and most
don't offer such tools now, every little off-shoot/whitebox
SDHC, CF, USB, etc... NAND) that the device is only 70% usable
from it's reported size.

--  
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: "Bryan J Smith" <b.j.smith at ieee.org>
Date: Fri, 9 Apr 2010 23:30:10 
To: James Ewing Cottrell 3rd<JECottrell3 at Comcast.NET>; <calug-bounces at unknownlamer.org>; Rajiv Gunja<opn.src.rocks at gmail.com>
Cc: CALUG<calug at unknownlamer.org>
Subject: Re: [CALUG] Can Media cards have bad blocks?

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
_______________________________________________
CALUG mailing list
CALUG at unknownlamer.org
http://lists.unknownlamer.org/listinfo/calug