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Date: Mon, 11 Jan 2010 15:26:15 -0800 From: "H. Peter Anvin" <hpa@...or.com> To: Pavel Machek <pavel@....cz> CC: Karel Zak <kzak@...hat.com>, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, util-linux-ng@...r.kernel.org Subject: Re: [ANNOUNCE] util-linux-ng v2.17 (stable) 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-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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