On Tuesday 21 March 2006 08:01, John Richard Moser wrote:
> I have a kind of dumb question. I keep hearing that "USB Flash Memory"
> or "Compact Flash Cards" and family have "a limited number of writes"
> and will eventually wear out. Recommendations like "DO NOT PUT A SWAP
> FILE ON USB MEMORY" have come out of this. In fact, quoting
> Documentation/laptop-mode.txt:
>
> * If you're worried about your data, you might want to consider using
> a USB memory stick or something like that as a "working area". (Be
> aware though that flash memory can only handle a limited number of
> writes, and overuse may wear out your memory stick pretty quickly.
> Do _not_ use journalling filesystems on flash memory sticks.)
>
> The question I have is, is this really significant? I have heard quoted
> that flash memory typically handles something like 3x10^18 writes; and
> that compact flash cards, USB drives, SD cards, and family typically
> have integrated control chipsets that include wear-leveling algorithms
> (built-in flash like in an iPaq does not; hence jffs2). Should we
> really care that in about 95 billion years the thing will wear out
> (assuming we write its entire capacity once a second)?
>
> I call FUD.
Search for a thread on LKML having to do with enabling "sync" on removable
media, especially VFAT media. If you are copying a large file, and the FAT
on the device is being updated with every block, you can literally fry your
device in a matter of minutes, because the FAT is always in the same spot,
thus it is always overwriting the same spot.
j----- k-----
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Joshua Kugler PGP Key: http://pgp.mit.edu/
CDE System Administrator ID 0xDB26D7CE
http://distance.uaf.edu/
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