Uwe Dippel wrote:
My point is that you have NO WAY of knowing that the data you "rescued" above is valid, unless you have some sort of out-of-band checksumming mechanism.[i]I don't understand why the rules for ZFS are any different from the rules for any other filesystem. Why don't you try pulling out drives for UFS and pcfs and seeing whether they are corrupted or not? Guess what, they are equally likely to be corrupted, but you simply wont be ablt to detect the corruption.As I said before, which one would you choose? Silent corruption or being notified that your data is inconsistent?[/i]Easy. I happen to be sysadmin, and my backups have to reliable. Yanking out a drive has happened here, somewhat frequently, though always unintentional, without proper umount. I have yanked a few, and so have my users. But I was - in the case of ext2/3 - always able to salvage enough, to copy the relevant data off that drive to a sane one. Always.
You seem to have answered my question above by saying you prefer silent data corruption. In the ZFS case it says, you've got corrupt data, and you then go back to your previous backup to recover. (Or are you saying that you only keep ONE backup?)
I am lucky enough to have been spared the misfortune described by some of our friends, of encountering an unrecoverable pool without export. Since the OP asked for removable backup, at least as sysadmin, I prefer ext3 any day. A file lost and a thousand saved is much better than 'sorry, but this pool has ceased to exist'.
You have no way of proving that the thousand saved are actually saved.
Good luck with that. I've been doing ZFS send/recv for a few years now without any problems and guaranteed lack of corruption. I don't think you can make the same claim.And that's what I do these days: adding a Linux-box to the network and save everything from my OpenSolaris-es nicely on a bunch of external ext3-drives. (Seeing eyes rolling and flames lighting up.)
Uwe
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