Messages in this thread | | | Date | Thu, 21 Jun 2007 13:00:35 -0400 | From | Mark Lord <> | Subject | Re: limits on raid |
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david@lang.hm wrote: > On Thu, 21 Jun 2007, David Chinner wrote: > >> On Thu, Jun 21, 2007 at 12:56:44PM +1000, Neil Brown wrote: >> >>> I have that - apparently naive - idea that drives use strong checksum, >>> and will never return bad data, only good data or an error. If this >>> isn't right, then it would really help to understand what the cause of >>> other failures are before working out how to handle them.... >> >> The drive is not the only source of errors, though. You could >> have a path problem that is corrupting random bits between the drive >> and the filesystem. So the data on the disk might be fine, and >> reading it via a redundant path might be all that is needed. > > one of the 'killer features' of zfs is that it does checksums of every > file on disk. so many people don't consider the disk infallable. > > several other filesystems also do checksums > > both bitkeeper and git do checksums of files to detect disk corruption
No, all of those checksums are to detect *filesystem* corruption, not device corruption (a mere side-effect).
> as david C points out there are many points in the path where the data > could get corrupted besides on the platter.
Yup, that too.
But drives either return good data, or an error.
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