cvs commit: src/sbin/atacontrol atacontrol.c

[Poul-Henning Kamp]

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 
>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 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.