If you don't do background scrubbing, you don't know about bad blocks in advance. If you're running RAID-Z, this means you'll lose data if a block is unreadable and another device goes bad. This is the point of scrubbing, it lets you repair the problem while you still have redundancy. :-)
Whether it's better to use 'zfs scrub' vs. reading the whole device depends on your environment. One issue with zfs scrub is that it generates effectively small random i/o. This is a good thing if you're in a heavily loaded environment, since the i/o can be scheduled amidst everything else. It's not a good thing if you're in a lightly loaded environment, since it's much slower than just reading the whole disk sequentially. So if, for instance, you have a "down time" at night (e.g. university environment), reading the whole device at that time would be more efficient. This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
