>Herb Peyerl wrote:
>
>> Hal Snyder <hal@vailsys.com>  wrote:
>>  > A question on the flash drive: do you have its filesystems mounted
>>  > read-only, or at least noatime? ISTR limits on the number of write
>>  > cycles for CF cards that would use them up after a few hours of
>>  > typical UNIX hard drive use.
>>
>> I haven't bothered with any such thing.  The flash I've been
>> encountering has a rewrite liftetime of a million cycles or something
>> on a per-bit basis... Since I have no swap configured and don't run
>> syslogd, I'm not too concerned with writes...
>
>Unless you are careful you could easily hit a million, with a write every
>10s it's less than 4 months.
>
>    -- Lennart


	Actually its not that much of a problem with good (1e6 write)
flash devices and correctly implemented wear leveling. The 1 million write
cycle limit is per block, so with wear leveling, the actual lifetime
depends on the free space. Say you have 4M free on that 32M flash: You
could then write and re-write a 4K file ~a billion times because the 4k
block is not always written to the same place, but rather different places
in the 4M free space because of the wear leveling.

	So if you have decent 1e6 write (probably NAND) flash and only
dribble 10k per sec or so to the flash and you have 4M or so free, a 10
year MTBF is not a problem...


	I've has a flash based NetBSD x86 system up for 1.5 years now with
0 trouble: 16M flash, 4M free, ~5K bytes per second average disk write
rate.


PCW