Bill Broadley <[EMAIL PROTECTED]> writes: > Leif Nixon wrote: >> Reconstruction. With raid 6, you can recover from single-disk >> corruption (As opposed to *failures*, where you get read errors from a >> disk. Raid 6 can handle two simultaneous disk *failures*.). >> See section 4 in: >> http://www.kernel.org/pub/linux/kernel/people/hpa/raid6.pdf >> > > I just read it. > >> Just recalculating the parity blocks does give you a consistent raid >> stripe, but destroys your data (unless it actually was one of the >> parity blocks that was corrupted). > > Er, that's not how I read it at all. To quote: > > In the case of data drive corruption, once the faulty drive has been > identified, recover using the P drive in the same way as a one-disk > erasure failure.
I think you misunderstood me. This quote is about how it *should* be done. My point is that as far as we can tell many raid controllers, as well as the current md driver, don't do this. If they find an inconsistent stripe they don't try to identify the corrupt block. Instead, they dumbly *recompute P and Q*, which of course makes the stripe consistent, but *leaves the corrupt data in place*. -- Leif Nixon - Systems expert ------------------------------------------------------------ National Supercomputer Centre - Linkoping University ------------------------------------------------------------ _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
