Re: [Patch] document ext3 requirements (was Re: [RFD] Incrementalfsck)

[Theodore Tso]

On Thu, Jan 17, 2008 at 04:31:48PM -0800, Bryan Henderson wrote:
> But I heard some years ago from a disk drive engineer that that is a myth 
> just like the rotational energy thing.  I added that to the discussion, 
> but admitted that I haven't actually seen a disk drive write a partial 
> sector.

Well, it would be impossible or at least very hard to see that in
practice, right?  My understanding is that drives do sector-level
checksums, so if there was a partially written sector, the checksum
would be bogus and the drive would return an error when you tried to
read from it.

> Ted brought up the separate issue of the host sending garbage to the disk 
> device because its own power is failing at the same time, which makes the 
> integrity at the disk level moot (or even undesirable, as you'd rather 
> write a bad sector than a good one with the wrong data).

Yep, exactly.  It would be interesting to see if this happens on
modern hardware; all of the evidence I've had for this is years old at
this point.  

							- Ted
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