Anton B. Rang wrote: > I find it naïve to imagine that Sun customers "expect" their UFS (or other) > file systems to be unrecoverable.
OK, I'll bite. If we believe the disk vendors who rate their disks as having an unrecoverable error rate of 1 bit per 10^14 bits read, and knowing that UFS has absolutely no data protection of its data, why would you think that it is naive to think that a disk system with UFS cannot lose data? Rather, I would say it has a distinctly calculable probability. Similarly, for ZFS, the checksum is not perfect, so there is a calculable probability that the ZFS checksum will not detect an unrecoverable (read) error. The difference is that the probability that ZFS will not detect an error is considerably smaller than that of UFS (or FAT, or HSFS, or ...) > Any case where fsck failed quickly became an escalation to the sustaining > engineering organization. Restoring from backup is almost never a > satisfactory answer for a commercial enterprise. > I agree. However, I've personally experienced well over 100 fsck failures over the years, and while I was always unsatisfied, I didn't always lose data[1]. When I did lose data, perhaps it was data I could live without, but that was my call. Would you rather that ZFS should simply say, "hey you lost some data, but we won't tell you where... ?" [1] once upon a time, I used a [vendor-name-elided] disk for a 2,300 user e-mail message store. I upgraded the OS, which implemented some new SCSI options. The disk's firmware didn't handle those options properly and would wait about 7 hours before corrupting the UFS file system containing the message store, requiring a full restore. So, how many shifts do you think it took to fail, recover, and ultimately resolve the disk firmware issue? Hint: the firmware rev arrived via UPS. Personally, I'm very glad that a file system has come along that verifies data... and that feature seems to be catching, as other file systems seem to be doing the same. Hopefully, in a few years silent data corruption will be a footnote on the lore of computing. -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
