On Wed, February 11, 2009 18:25, Toby Thain wrote: > > Absolutely. You should never get "actual corruption" (inconsistency) > at any time *except* in the case Jeff Bonwick explained: i.e. faulty/ > misbehaving hardware! (That's one meaning of "always consistent on > disk".) > > I think this is well understood, is it not?
Perhaps. I think the consensus seems to be settling down this direction (as I filter for reliability of people posting, not by raw count :-)). The shocker is how much hardware that doesn't behave to spec in this area seems to be out there -- or so people claim; the other problem is that we can't sort out which is which. > Write barriers are not a new concept, and nor is the necessity. For > example, they are a clearly described feature of DEC's MSCP > protocol*, long before ATA or SCSI - presumably so that transactional > systems could actually be built at all. Devices were held to a high > standard of conformance since DEC's customers (like Sun's) were > traditionally those whose data was of very high value. Storage > engineers across the industry were certainly implementing them long > before MSCP. > > --Toby > > > * - The related patent that I am looking at is #4,449,182, filed 5 > Oct, 1981. > "Interface between a pair of processors, such as host and peripheral- > controlling processors in data processing systems." While I was working for LCG in Marlboro, in fact. (Not on hardware, nowhere near that work.) -- David Dyer-Bennet, d...@dd-b.net; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
