From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?B?U3TDqXBoYW5lIEFOQ0VMT1Q=?= Subject: Re: Compact Flash Question Date: Wed, 07 May 2008 17:01:54 +0200 Message-ID: <4821C462.2000108@free.fr> References: <48215673.3060201@wpkg.org> <48216039.3070001@wpkg.org> <4821A12F.2020800@aitel.hist.no> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <4821A12F.2020800@aitel.hist.no> Sender: linux-kernel-owner@vger.kernel.org To: Helge Hafting Cc: Tomasz Chmielewski , Bart Van Assche , LKML , YSadgat1@gcte.com, linux-os@analogic.com, Alan , Linux IDE List-Id: linux-ide@vger.kernel.org experience report : In June 2004 we migrated to CF after bad hard disk crashes experience..= =2E Most of the CF do NOT do wear leveling, you have to ask the manufacture= r if it does it or not, generally it is called industrial... and normally= , cost much more . So, for low cost cf I assume you have to do wear leveling with the kernel ...otherwise it is already "wear leveling inside" Since the technology evolves very fast it may be possible today that th= e production's cost of wear leveled CF will be the same as standard one and wear leveling will be a standard ? I think it should be possible to know if the Cf supports wear leveling using the the identify device command (0xEC) and look at words 82 to 87= =20 (cf. CF specifications http://www.compactflash.org/specdl1.htm) Depending on the application, some system hacks like noatime... need to be setted up. we use silicon systems CF with wear leveling inside , we write a few kb data back each 1/4 h on it.(log /tmp files are redirected to ram) Since June 2004 ALL hard disk systems based replaced with CF (env. 10= 0 units) have not failed. If somebody could report experience with other brand CF including wear leveling , it will be fine some other brand I know only the name : www.apro-tw.com http://www.afaya.com.tw/ (spec tells it supports wear leveling) Best Regards S.Ancelot Helge Hafting a =C3=A9crit : > Tomasz Chmielewski wrote: >> >> How does it work, then? >> How can it do wear levelling over the whole CF if some (or most) are= a >> of CF is already used by our precious data/metadata? >> It would have to know the areas where no data is stored, but it >> contradicts the CF <-> filesystem separation. > It don't necessarily need to know. It can swap two used blocks, one > often-used and one > rarely-used. That way the rarely-used block is rewriten over the > previously busy > block, and the busy block is moved to the rarely used area that isn't > worn. > This implies an extra write whenever a busy block is moved. Don't > know if > anybody do this, but the technique is simple enough. > > CF-filesystem separation is necessary, for they can't know in advance > what > filesystem or partitioning scheme will be used. (I have ext3 on CF, > for example...) > > Helge Hafting > > > --=20 > To unsubscribe from this list: send the line "unsubscribe > linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > >