Re: [ILUG] VIA EPIA server   | From: Timothy Murphy 
  | Date: Mon, 8 Oct 2007 19:10:03 +0100
  | 
  | On Mon 08 Oct 2007, Conor Daly wrote:
  | > What do you do about frequently written files?
  | > Don't these tend to age the flash card?
  | > Or am I just so behind current flash technology?
  | 
  | Well, you couldn't be further behind than me.
  | Do flash cards get tired?
  | Are IDE flash disks any different?

 yes and no.  both get âtiredâ but there may be (but not
 definitely always is?) a difference.

 it doesn't matter how you package the FLASH, as a card,
 stick, drive with IDE, or whatever.  each sector in the
 FLASH (which are much larger than disc sectors) has a
 finite number of erase-write cycles.

 what that number _is_ varies all over the map, depending
 on the technology (NOR or NAND FLASH), manufacturer, &tc.
 AFAICR, some manufacturers only provide guarantees for
 certain sectors (e.g., 0).  numbers I've recall seeing
 range from 100,000 cycles to something around one million;
 the back-of-envelope number I've used for many years is a
 maximum of 250,000 reliable erase-write cycles per sector.

 what some IDEs or drivers do is âwear levellingâ, which
 distributes disc-blocks by dynamic remapping to different
 FLASH-sectors.  AFAICR, wear-levelling is proactive.

 some IDEs (or drivers?) are also(?) reactive, doing bad
 spot management.  if the just-written block(? sector?)
 doesn't read back correctly (a cheap check if done by
 the IDE (drive firmware)) it's then rewritten to
 another sector.  (I've no experience with this sort of
 FLASH bad spot management, so I'm hazy on the details.)

 hence, FLASH packaged as an IDE drive won't necessarily
 have the same write-lifetime problems as, say, a card,
 even though both use the same underlying limited-write
 storage technology.

cheers!
	-blf-
-- 
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