Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-21 Thread Chris Murphy
On Wed, Oct 21, 2015 at 2:07 PM, Austin S Hemmelgarn wrote: > And I realize of course right after sending this that my other reply didn't > get through because GMail refuses to send mail in plain text, no matter how > hard I beat it over the head... In the web browser

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-21 Thread Austin S Hemmelgarn
On 2015-10-21 12:01, Chris Murphy wrote: On Wed, Oct 21, 2015 at 2:07 PM, Austin S Hemmelgarn wrote: And I realize of course right after sending this that my other reply didn't get through because GMail refuses to send mail in plain text, no matter how hard I beat it over

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-21 Thread Austin S Hemmelgarn
On 2015-10-20 15:59, Austin S Hemmelgarn wrote: On 2015-10-20 15:20, Duncan wrote: Yes, there's some small but not infinitesimal chance the checksum may be wrong, but if there's two copies of the data and the checksum on one is wrong while the checksum on the other verifies... yes, there's

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-21 Thread Austin S Hemmelgarn
On 2015-10-21 07:51, Austin S Hemmelgarn wrote: On 2015-10-20 15:59, Austin S Hemmelgarn wrote: On 2015-10-20 15:20, Duncan wrote: Yes, there's some small but not infinitesimal chance the checksum may be wrong, but if there's two copies of the data and the checksum on one is wrong while the

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-20 Thread Austin S Hemmelgarn
On 2015-10-20 09:15, Russell Coker wrote: On Wed, 21 Oct 2015 12:00:59 AM Austin S Hemmelgarn wrote: https://www.gnu.org/software/ddrescue/ At this stage I would use ddrescue or something similar to copy data from the failing disk to a fresh disk, then do a BTRFS scrub to regenerate the

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-20 Thread Duncan
Austin S Hemmelgarn posted on Tue, 20 Oct 2015 09:59:17 -0400 as excerpted: >>> It is worth clarifying also that: >>> a. While BTRFS will not return bad data in this case, it also won't >>> automatically repair the corruption. >> >> Really? If so I think that's a bug in BTRFS. When mounted rw

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-20 Thread Duncan
james harvey posted on Tue, 20 Oct 2015 00:16:15 -0400 as excerpted: > Background - > > My fileserver had a "bad event" last week. Shut it down normally to add > a new hard drive, and it would no longer post. Tried about 50 times, > doing the typical everything non-essential unplugged,

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-20 Thread Austin S Hemmelgarn
On 2015-10-20 14:54, Duncan wrote: But tho I'm a user not a dev and thus haven't actually checked the source code itself, my believe here is with Russ and disagrees with Austin, as based on what I've read both on the wiki and seen here previously, btrfs runtime (that is, not during scrub)

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-20 Thread Austin S Hemmelgarn
On 2015-10-20 15:20, Duncan wrote: Austin S Hemmelgarn posted on Tue, 20 Oct 2015 09:59:17 -0400 as excerpted: It is worth clarifying also that: a. While BTRFS will not return bad data in this case, it also won't automatically repair the corruption. Really? If so I think that's a bug in

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-20 Thread Tim Walberg
On 10/20/2015 15:59 -0400, Austin S Hemmelgarn wrote: >> . >> With a 32-bit checksum and a 4k block (the math is easier with >> smaller numbers), that's 4128 bits, which means that a random >> single bit error will have a approximately 0.24% chance of >> occurring

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-20 Thread Duncan
Austin S Hemmelgarn posted on Tue, 20 Oct 2015 15:48:07 -0400 as excerpted: > FWIW, my assessment is based on some testing I did a while back (kernel > 3.14 IIRC) using a VM. The (significantly summarized of course) > procedure I used was: > 1. Create a basic minimalistic Linux system in a VM

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-20 Thread Austin S Hemmelgarn
On 2015-10-20 00:45, Russell Coker wrote: On Tue, 20 Oct 2015 03:16:15 PM james harvey wrote: sda appears to be going bad, with my low threshold of "going bad", and will be replaced ASAP. It just developed 16 reallocated sectors, and has 40 current pending sectors. I'm currently running a

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-20 Thread Russell Coker
On Wed, 21 Oct 2015 12:00:59 AM Austin S Hemmelgarn wrote: > > https://www.gnu.org/software/ddrescue/ > > > > At this stage I would use ddrescue or something similar to copy data from > > the failing disk to a fresh disk, then do a BTRFS scrub to regenerate > > the missing data. > > > > I

Expected behavior of bad sectors on one drive in a RAID1

2015-10-19 Thread james harvey
Background - My fileserver had a "bad event" last week. Shut it down normally to add a new hard drive, and it would no longer post. Tried about 50 times, doing the typical everything non-essential unplugged, trying 1 of 4 memory modules at a time, and 1 of 2 processors at a time. Got no

Re: Expected behavior of bad sectors on one drive in a RAID1

2015-10-19 Thread Russell Coker
On Tue, 20 Oct 2015 03:16:15 PM james harvey wrote: > sda appears to be going bad, with my low threshold of "going bad", and > will be replaced ASAP. It just developed 16 reallocated sectors, and > has 40 current pending sectors. > > I'm currently running a "btrfs scrub start -B -d -r /terra",