On Mon, Sep 14, 2009 at 01:18:55PM -0500, Stephen Johnson wrote: Flash again
(maybe somebody indeed has found _HARD_ data about wear leveling, something like "there are no more flash chips available today that lack an in-hardware-implementation of wearleveling" would be reassuring and down-right *dreamy*; if you'd success here, please drop us a line:)) > When people think about the ramifications of writing over a TB of data > to handheld PDA, they realize their fears were a bit silly. I'll admit I > was worried about wearing out the flash of my IPAQ before I did the > math. Even reflashing it a few hundred times, the IPAQ would be obsolete > long before I wore out the flash in it. IF and ONLY IF there's some kind of wear-leveling active that spreads out hotspots over all the flash "pages" (or at least some kind of reserve-page substitution or just even bad block marking). Or your write patterns has similar characteristics. Like log-structured file-systems or reflashing firmware. And for this case, the TB you mention is easily more than enough. Granted that the more expensive sata-ssd shoudl implement at least one of these (proprietary mumble <unnamed> mumble) counter-measures. But hotspots or swap hitting the same logical sector all the time? Changing 512B all the time, requiring write/erase cycles all the time on the same cell. (what are the numbers here: 100K cycles, 1M at best for the most expensive?) Consider USB sticks and directly soldered-in flash in small and still expensive gizmos. Gizmos naturally without any mention of anything at all in available docs wrt flash and wear-leveling? Consider FAT and it's tendency of hot spots and it's unhappy marriage to stupid bad old flash - I'd still suspect that as the reason for the death my old creative muvo... Is it indeed safe nowadays to assume that some basic wear leveling is implemented at HW-LEVEL in say HTC androids or Nokia's N900-to-be - so I can really place ordinary swap and logs on flash without having to consider/add work-arounds against hotspots? Merely finding hints online that wearleveling on flash has been known in the mid-nineties doesn't convince me this issue is indeed ancient history. Doubly so for mass-market consumer/prosumer-grade stuff, where builtin obsolescence is a marketing device. still sceptical, -- cu Peter [email protected] _______________________________________________ Discuss mailing list [email protected] http://lopsa.org/cgi-bin/mailman/listinfo/discuss This list provided by the League of Professional System Administrators http://lopsa.org/
