Date: Mon, 17 Dec 2007 14:55:31 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: "Bruce M. Simpson" <bms@incunabulum.net> Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, "Bruce M. Simpson" <bms@FreeBSD.org>, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sbin/atacontrol atacontrol.c Message-ID: <11419.1197903331@critter.freebsd.dk> In-Reply-To: Your message of "Mon, 17 Dec 2007 14:43:55 GMT." <47668B2B.5030206@incunabulum.net>
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In message <47668B2B.5030206@incunabulum.net>, "Bruce M. Simpson" writes: >Poul-Henning Kamp wrote: >> I have the attached patch in sos@ mailbox for approval, that adds >> BIO_DELETE support for the ata driver. >> >> I also want to implement a -E option to fsck(8) to erase all >> unallocated blocks. >> >> And finally the big item: msdosfs and ufs support to issue BIO_DELETE >> when files are deleted. UFS is nasty because of soft-updates. >> > >Aha, I understand now. CFA and SATA vendors have gone off in two >separate directions: > * PATA and SATA drives, for a few years now, have tended to rewrite one >cylinder at a time, which implies erasing the data on that cylinder. Everybody denies this in the stongest possibly way whenever I ask them, so far I have not seen this claim substantiated by any fact or person who would be in a position to know. > * NAND Flash devices should not have their sectors erased unless >absolutely necessary, to implement wear levelling. Wrong, almost exactly the opposite in fact: Flash devices using wear-levelling should have data erased as soon as possible to give the wear-levelling the maximum amount of information and available space to work with. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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