Crashed gmirror, single disk marked SYNC and wont boot...

Pawel Jakub Dawidek pjd at
Tue Aug 21 08:00:15 PDT 2007

On Tue, Aug 21, 2007 at 02:15:08PM +0200, Johan Ström wrote:
> Hi
> FreeBSD 6.2-RELEASE-p1 FreeBSD 6.2-RELEASE-p1 #7:  
> Tue Feb 13 18:24:34 CET 2007     johan at 
> src/sys/ROUTER.POLLING  i386
> IPSEC, also pfsync and carp)
> This weekend I had a disk failing on me in a machine running gmirror  
> gm0 with 2 providers (ad0 and ad6). The whole box froze with no  
> screen output, and on hard reboot I got some LBA errors etc from ad0,  
> after a few reboots it got up and running though (I wasnt at the  
> screen, had do do it by phone so couldn't really debug very well).
> As soon as the box got up, I removed ad0 from the gmirror, so ad6 was  
> the only provider. Today I got a new disk that would replace ad0..
> Now remeber, ad6 was the only disk in the mirror. I took the box down  
> fine, replaced the disk. ad0 was now gone and instead I hade ad4 (ad4 
> +6 is SATA, ad0 was IDE). Changed so I booted of the old SATA..   
> Okay, there came the first problem; the boot loader gave me the usual  
> options F1 FreeBSD F5 Disk 2 (or whatever it said).. If I pressed F1  
> i got the same prompt again.. F5 nothing at all.. Funny!... The  
> system refused to load the loader (or whatever the 1-9 menu thingy is  
> called) kernel or anything..
> So I finally plugged the old ad0 disk into the machine to at least  
> get it booted, thinking it would go up on the gmirror.. Nope..:
> (got the new ad4 out here)
> ad0: 38166MB <WDC WD400BB-00CAA1 17.07W17> at ata0-master UDMA100
> ad6: 152627MB <SAMSUNG HD160JJ ZM100-41> at ata3-master SATA150
> GEOM_MIRROR: Device gm0 created (id=4029378995).
> GEOM_MIRROR: Device gm0: provider ad6 detected.
> Root mount waiting for: GMIRROR
> Root mount waiting for: GMIRROR
> Root mount waiting for: GMIRROR
> Root mount waiting for: GMIRROR
> GEOM_MIRROR: Force device gm0 start due to timeout.
> Trying to mount root from ufs:/dev/mirror/gm0s1a
> Manual root filesystem specification:
>   <fstype>:<device>  Mount <device> using filesystem <fstype>
>                        eg. ufs:da0s1a
>   ?                  List valid disk boot devices
>   <empty line>       Abort manual input
> mountroot>
> Okey... so why wouldnt it load my mirror from ad6 now?? I just did a  
> clean shutdown without problems.. It didnt even recognize any slices  
> on ad6s1 (altough the ad6s1 was found)...

It loaded your mirror just fine, you confuse things. Gmirror started in
degraded state, as one could expect, but it seems there is no 'a'
partition on your gm0s1 slice (or entire bsdlabel is gone).
You could try to recreate it based on bsdlabel from ad0 (if it should be
the same), but I've no idea how it disapeared. Anyway, gmirror seems to
work properly.

> Some more digging into gmirror, I did a gmirror dump ad6:
> Metadata on /dev/ad6:
>      magic: GEOM::MIRROR
>    version: 3
>       name: gm0
>        mid: 4029378995
>        did: 449032193
>        all: 3

You have 3-way mirror?

>      genid: 0
>     syncid: 5
>   priority: 0
>      slice: 4096
>    balance: round-robin
> mediasize: 20416757248
> sectorsize: 512
> syncoffset: 0
>     mflags: NONE
>     dflags: SYNCHRONIZING
> hcprovider:
>   provsize: 160041885696
>   MD5 hash: 6e1e8ca80a27e0e1b0460feab595c39f

BTW. Your provider size is 149GB and mirror only use 19GB, which means
you mirrored 149GB disk with 19GB disk and you waste 130GB (it's

> Some googling indicated  that  SYNCHRONIZING means that its not  
> "complete" and wont mount? Is that correct? Why would it be in that  
> state then, I just shut it down fine... And where the f*ck did my  
> slices go??..

SYNCHRONIZING means that this component was/is being synchronized. It
seems that you removed/lost the master disk, while it was synchronizing.
It should work anyway.

BTW. You confuse things again. Your slice is just fine (ad6s1), you
don't have partitions, AFAIU.

All in all, your partition table seems to be gone. If you created it on
gmirror before (gm0s1) you may still have the same partition table on
the other half of the mirror. You can try to move it to ad6 with
bsdlabel and verify if you can see file system inside partitions.

Pawel Jakub Dawidek             
pjd at                 
FreeBSD committer                         Am I Evil? Yes, I Am!
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