Messages in this thread | | | From | "Martin Eriksson" <> | Subject | Re: Journaling pointless with today's hard disks? | Date | Tue, 27 Nov 2001 00:49:19 +0100 |
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----- Original Message ----- From: "Steve Brueggeman" <xioborg@yahoo.com> To: <linux-kernel@vger.kernel.org> Sent: Monday, November 26, 2001 7:05 PM Subject: Re: Journaling pointless with today's hard disks?
<snip>
> >There is no "power monitor" in a PC system (at least not that is visible > >to the drive) -- if the drive needs it, it has to provide it itself. > > > >It's definitely the responsibility of the drive to recover gracefully > >from such an event, which means that it writes anything that it has > >committed to the host to write; > Correct. If a write gets interrupted in the middle of it's operation, > it has not yet returned any completion status, (unless you've enabled > write-caching, in which case, you're already asking for trouble) A > subsequent read of this half-written sector can return uncorrectable > status though, which would be unfortunate if this sector was your > allocation table, and the write was a read-modify-write. > > >anything it hasn't gotten committed to > >write (but has received) can be written or not written, but must not > >cause a failure of the drive. > Reading a sector that was a partial-write because of a power-loss, and > returning UNCORRECTABLE status, is not a failure of the drive.
I sure think the drives could afford the teeny-weeny cost of a power failure detection unit, that when a power loss/sway is detected, halts all operations to the platters except for the writing of the current sector.
_____________________________________________________ | Martin Eriksson <nitrax@giron.wox.org> | MSc CSE student, department of Computing Science | Umeå University, Sweden
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