On Thu, 9 Oct 2014 12:55:50 +0100 Hugo Mills <h...@carfax.org.uk> wrote:
> On Thu, Oct 09, 2014 at 11:53:23AM +0000, Duncan wrote: > > Austin S Hemmelgarn posted on Thu, 09 Oct 2014 07:29:23 -0400 as > > excerpted: > > > > > Also, you should be running btrfs scrub regularly to correct > > > bit-rot and force remapping of blocks with read errors. While > > > BTRFS technically handles both transparently on reads, it only > > > corrects thing on disk when you do a scrub. > > > > AFAIK that isn't quite correct. Currently, the number of copies is > > limited to two, meaning if one of the two is bad, there's a 50% > > chance of btrfs reading the good one on first try. > > Scrub checks both copies, though. It's ordinary reads that don't. While I believe I was clear in full context (see below), agreed. I was talking about normal reads in the above, not scrub, as the full quote should make clear. I guess I could have made it clearer in the immediate context, however. Thanks. > > Thus, while btrfs may randomly bump into a bad block and rewrite it > > with the good copy, scrub is the only way to systematically detect > > and (if there's a good copy) fix these checksum errors. -- Duncan - No HTML messages please, as they are filtered as spam. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
