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SubjectRe: [Patch] document ext3 requirements (was Re: [RFD] Incremental fsck)
Ric Wheeler wrote:
> Theodore Tso wrote:
>> 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.
> There is extensive per sector error correction on each sector written.
> What you would see in this case (or many, many other possible ways
> drives can corrupt media) is a "media error" on the next read.


> You would never get back the partially written contents of that sector
> at the host.


> Having our tools (fsck especially) be resilient in the face of media
> errors is really critical. Although I don't think the scenario of a
> partially written sector is common, media errors in general are common
> and can develop over time.



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