From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [ANNOUNCE] util-linux-ng v2.17 (stable) Date: Mon, 11 Jan 2010 15:26:15 -0800 Message-ID: <4B4BB397.5090500@zytor.com> References: <20100108093302.GS1969@nb.net.home> <4B47A713.9060405@zytor.com> <20100111140255.GA1416@ucw.cz> <4B4B5768.2040005@zytor.com> <20100111201734.GA11674@elf.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Karel Zak , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, util-linux-ng-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Pavel Machek Return-path: In-Reply-To: <20100111201734.GA11674-I/5MKhXcvmPrBKCeMvbIDA@public.gmane.org> Sender: util-linux-ng-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org 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 util-linux-ng" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html