> 1) When I notice an error in a file that I've copied from a ZFS disk I > want to know whether that error is also in the original file on my ZFS > disk or if it's only in the copy.
This was already addressed but let me do so slightly differently: One of the major points of ZFS checksumming is that, in the abscence of software bugs or hardware memory corruption issues when the file is read on the host, successfully reading a file is supposed to mean that you got the correct version of the file (either from physical disk or from cache, having previously been read from physical disk). A scrub is still required if you want to make sure the file is okay *ON DISK*, unless you can satisfy yourself that no relevant data is cached somewhere (or unless someone can inform me of a way to nuke a particular file and related resources from cache). > Up to now I've been storing md5sums for all files, but keeping the > files and their md5sums synchronized is a burden I could do without. FWIW I wanted to mention here that if you care a lot about this, I'd recommend something like par2[1] instead. It uses forward error correction[2], allowing you to not only detect corruption, but also correct it. You can choose your desired level of redundancy expressed as a percentage of the file size. [1] http://en.wikipedia.org/wiki/Parchive [2] http://en.wikipedia.org/wiki/Forward_error_correction -- / Peter Schuller PGP userID: 0xE9758B7D or 'Peter Schuller <[EMAIL PROTECTED]>' Key retrieval: Send an E-Mail to [EMAIL PROTECTED] E-Mail: [EMAIL PROTECTED] Web: http://www.scode.org
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