> RAID level what? How is anything salvagable if you > lose your only copy? [ ... ] > > ZFS does store multiple copies of metadata in a > single vdev, so I > assume we're talking about data here.
I believe we're talking about metadata, as that is the case where ZFS reports that the pool (as opposed to a dataset) is corrupt. On a UFS file system, if the superblock is bad, the entire file system would be lost; but the fsck utility can use an alternate copy. On most other file systems, there is sufficient redundancy within the file system that metadata damage results in the loss of only a fraction of data. ZFS, in fact, also has sufficient redundancy to allow this, I believe. However, there is not currently a file system checker which exploits this to alow a damaged pool to be recovered. ZFS does keep two or three copies of its metadata, and it seems highly unlikely that both or all three of these would be damaged without easily noticeable error rates (and data being affected much more quickly, simply because there are more data blocks than metadata). It seems likely that a corrupted pool, then, is *not* likely the result of hardware problems, or at least not hardware problems which affect all reads or writes independently. This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
