Hello PFC, Friday, March 24, 2006, 7:07:04 PM, you wrote: P> I think you would like something like this : P> A LVM (or dm- device mapper) layer which sits between the RAID layer and P> the physical disks. This layer computes checksums as data is written to P> the physical disks, and checks read data against these checksums. P> Problem is, where do you store the checksums ? Why not store the checksums on the same device that stores the blocks? For example, let a 64-kb (65536b) block of data store, say, 65520 bytes of data and 16 bytes of checksum/digest and a timestamp. If the hardware goes crazy and some bits (or more) are mixed up, we can detect if the data is not trustworthy - the checksum and/or data is screwed and they don't match each other. A drawback is the impossibility to mount such a device as-is, and some loss of performance in addressing/buffering which I think is okay as a tradeoff for reliability. A good thing (arguably) would be a capability of raid1 layer to interact with this checksummed layer during rebuilds or even casual work. If a block is found to be bad on one submirror, it could be read (and re-written) from another, valid, copy without remaking the whole metadevice. -- Best regards, Jim Klimov mailto:klimov@xxxxxxxxxxx - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
