Re: error count

[Chris Samuel <chris@csamuel.org>]

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On Sat, 10 Aug 2013 07:19:27 PM Russell Coker wrote:

> But what does generation_errs mean?  I'm seeing some on one system.  
> Should I be concerned?  If I write a Nagios check which ones should be 
> warnings and which ones errors?

All I know is that ioctl.h says:

BTRFS_DEV_STAT_GENERATION_ERRS, /* an indication that blocks have not
                                                           * been written */

Looking at the kernel code that only seems to get incremented during a scrub.  
The code that does that says:

                } else if (generation != le64_to_cpu(h->generation)) {
                        sblock->header_error = 1;
                        sblock->generation_error = 1;
                }

The generation there is from the btrfs inode structure, the header says:

        /* full 64 bit generation number, struct vfs_inode doesn't have a big
         * enough field for this.
         */
        u64 generation;


The wiki says:

https://btrfs.wiki.kernel.org/index.php/Glossary

# generation 
#   An internal counter which updates for each transaction. When a
# metadata block is written (using copy on write), current generation
# is stored in the block, so that blocks which are too new (and hence
# possibly inconsistent) can be identified.

and:

https://btrfs.wiki.kernel.org/index.php/Btrfs_design

# Everything that points to a btree block also stores the generation
# field it expects that block to have. This allows Btrfs to detect
# phantom or misplaced writes on the media.

HTH!

> Also why does it give the following errors about trying to open /dev/sr0
> when  using a BTRFS RAID-1 filesystem?  Below is for a RAID-1 over /dev/sdb
> and /dev/sdc.

I don't get that here, I'm building btrfs-progs from git at commit 
194aa4a1bd6447bb545286d0bcb0b0be8204d79f (July 5th), aka:

btrfs-progs$ git describe --tags
v0.20-rc1-358-g194aa4a

cheers!
Chris
-- 
 Chris Samuel  :  http://www.csamuel.org/  :  Melbourne, VIC

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