cvs commit: src/sbin/atacontrol atacontrol.c
phk at phk.freebsd.dk
Mon Dec 17 06:55:33 PST 2007
In message <47668B2B.5030206 at 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
> * 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 at 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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