I apologize for in effect suggesting that which was previously suggested in an earlier thread:
http://mail.opensolaris.org/pipermail/zfs-discuss/2008-March/046234.html And discovering that the feature to attempt worst case single bit recovery had apparently already been present in some form in an earlier development version of zfs, but removed for some illogical reason claiming that it masked programming errors (which makes no sense to me), and correspondingly recognized by other sun engineers that single bit errors may in fact be injected by various elements of the system which may touch the data beyond the drives themselves such as cpu's for example. I don't know where it comes from but there seems to be a standing assumption that most checksum errors are in fact multi-bit (some statistical testing should be able to determine if this is the case or not); personally I suspect the opposite, as drives tend to do a fairly good job of identifying uncorrectable data, therefore tend not to erroneously return garbage as being good, and the remaining hardware in most systems will not tend to generate sporadic multi-bit errors in greater frequency than single bit ones, therefore logical to assume that most data corruption will originate as single bit errors, which however if not detected and corrected may subsequently be utilized in calculations yielding potentially substantially more catastrophic results (which likely contribute to some percentage of wrong blocks being read/written, and subsequently mistaken as a resulting multi-bit data block error). Overall please reconsider re-incorporating this feature to be minimally enabled upon request if not default, as although worst case recovery of large block file data may be resource intensive, it would only be invoked as a last resort, with the alternative being a catastrophic loss of data which seems wholly unacceptable if in fact recoverable in place. This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
