On 01/11/2010 12:17 PM, Pavel Machek wrote: >> >> Uhm, that's just plain wrong. >> >> It doesn't matter if there is a "special mapping layer" -- if you're >> crossing multiple erase blocks you're still having more churn in >> your flash translation layer, with more wear on the device, and >> lower performance than if you didn't. > > Eraseblocks really should not matter. It is not as if each logical > sector belongs to one eraseblock.... > > (OTOH, maybe the eraseblock *groups* that are basis for wear-leveling > do, or maybe firmware is doing something really really strange.) > Pavel Maybe they "should not" matter, but they *do* matter. In most existing FTLs, each logical sector *does* belong to one erase block, although which particular erase block that is of course moves around. However, the invariant that matters though -- and the reason alignment matters -- is that for most FTLs, the *offset* of any particular logical sector within the erase block it currently belongs to is invariant, i.e. the FTL operates on physical sectors which are the same size as the erase blocks. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
