fsck / GEOM / Editing files in mirror partitions separately

[Julian Elischer]

On 10/10/14, 10:03 AM, Stephan Wehner wrote:
> Hello there,
>
> I have a FreeBSD 10.0-RELEASE-p7 system with system specifics:
>
> $ mount
> /dev/mirror/gm0s1a on / (ufs, local, journaled soft-updates)
> devfs on /dev (devfs, local, multilabel)
> /dev/mirror/gm0s1b on /home (ufs, local, journaled soft-updates)
> procfs on /proc (procfs, local)
>
> $ gmirror status
>        Name    Status  Components
> mirror/gm0  COMPLETE  ada0 (ACTIVE)
>                        ada1 (ACTIVE)
>
> $ gpart show
> =>        63  3907029104  mirror/gm0  MBR  (1.8T)
>            63  3907029042           1  freebsd  [active]  (1.8T)
>    3907029105          62              - free -  (31K)
>
> =>         0  3907029042  mirror/gm0s1  BSD  (1.8T)
>             0  2456848384             1  freebsd-ufs  (1.1T)
>    2456848384  1433600000             2  freebsd-ufs  (684G)
>   3890448384    16580658             4  freebsd-swap  (7.9G)
>
> Computer was rebooted by simply turning it off. On reboot, I got
> message "error aborting boot enter full pathname or shell or return
> for /bin/sh"
>
> First question: Is it normal that the filesystem will not survive a
> power loss, so that manual intervention is needed?
> I thought UFS would be more robust.
>
> Now I did something that may have been a bad idea.
>
> I ran fsck on both partitions of the mirror separately, I think they
> were called ad4s1 and ad6s1. For both it reported some problems to
> fix, and I did Y until they were declared "CLEAN."
>
> Then I mounted each partition separately, and made the same changes to
> a single text file (the file was identical in each partition).
but you PROBABLY have different metadata blocks
i.e. the timestamps will be different, and inodes may have been 
allocated in different places etc.


> Then rebooted, and now the system is running fine.
>
> Second question. Is that mirror in good shape? Is there a way to test?
I doubt it is in good shape though it may THINK it's in good shape.

to test.. boot of a third device (USB?) and compare the drives.
you will probably find differences..
  (your choice of how to compare the physical devices..)


>
> Third question. Does one even run fsck on partitions that are then
> controlled by geom?
>
> This shows in dmesg:
>
> GEOM_MIRROR: Device mirror/gm0 launched (1/2).
> GEOM_MIRROR: Device gm0: rebuilding provider ada0.
> GEOM_MIRROR: Device gm0: rebuilding provider ada0 finished.
> GEOM_MIRROR: Device mirror/gm0 launched (2/2).
how long did it take the do the above?  might it have copied one drive 
to another?
if so then you are ok..  (I do not use gmirror myself)
>
> Thanks,
>
> Stephan
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