Ext3 and RAID: silent data killers?
Posted Aug 31, 2009 22:45 UTC (Mon) by pizza (subscriber, #46)
Granted, that "firmware" may be in the form fo mask ROM, but I know of at least one case where a CF card had a firmware update released for it.
SD and MS are a lot simpler, but even they require something to translate the SD/MS wire protocols into flash read/write ops.
Posted Aug 31, 2009 22:52 UTC (Mon) by email@example.com (✭ supporter ✭, #52701)
Posted Aug 31, 2009 23:27 UTC (Mon) by drag (subscriber, #31333)
They all are 'smart devices'.
If it was not for the firmware MTD-to-Block translation then you could not use them in Windows and they could not be formatted Fat32.
When I have dealt with Flash in the past, the raw flash type, the flash just appears as a memory region. Like I have this old i386 board I am dealing with that has it's flash just starting at 0x80000 and it goes on for about eight megs or so.
That's it. That's all the hardware does for you. You have to know then how to communicate with it and it's underlining structure and know the proper way to write to it and everything. All that has to be done in software.
I suppose most of that is rather old fashioned.. the flash was soldiered directly into the traces on the board.
I can imagine it would be quite difficult and would require new hardware protocols to allow a OS to manage flash directly properly over something like SATA or USB.
But fundamentally MTD are quite a bit different from Block devices. It's a different class of I/O completely. Just like how a character device like a mouse or a keyboard can't be written to with Fat32. You can fake MTD by running a Block-to-MTD layer on SD flash or a file or anything else and some poeple think that helps with wear leveling, but I think that is foolish and may actually end up being self-defeating as you have no idea how the algorithms in the firmware work.
Posted Aug 31, 2009 23:59 UTC (Mon) by BenHutchings (subscriber, #37955)
AND SD and Memorystick and any other remotely consumer-related device.
They all are 'smart devices'.
Not all. SmartMedia, xD and Memory Stick variants provide a raw flash interface - that's a major reason why they have had to be revised repeatedly to allow for higher-capacity chips. They rely on an external controller to do write-buffering, and do not support any wear-leveling layer.
When I have dealt with Flash in the past, the raw flash type, the flash just appears as a memory region
It is possible for a flash controller to map NOR flash into memory since it is random-access for reading. However, large flash chips are all NAND flash which only supports block reads.
Posted Sep 1, 2009 0:00 UTC (Tue) by firstname.lastname@example.org (✭ supporter ✭, #52701)
Posted Sep 1, 2009 0:52 UTC (Tue) by drag (subscriber, #31333)
Remember that SD stands for 'Secure Digital' and is DRM'd. So there has to be some smarts in it to do that.
Posted Sep 1, 2009 6:22 UTC (Tue) by Los__D (guest, #15263)
(Still doesn't change the point, though. SDs are probably designed with internal firmware)
Posted Sep 1, 2009 9:36 UTC (Tue) by alonz (subscriber, #815)
As for firmware, the SD card interface (available for free at www.sdcard.org defines accesses in terms of 512-byte “logical” sectors, practically mandating the card to implement a flash translation layer.
Posted Sep 1, 2009 12:49 UTC (Tue) by Los__D (guest, #15263)
I read "devices" as the SD cards themselves.
Posted Sep 1, 2009 16:57 UTC (Tue) by Baylink (guest, #755)
Posted Sep 1, 2009 17:37 UTC (Tue) by iabervon (subscriber, #722)
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