# gmirror - cannot add good disk when failed disk is online



## achix (May 18, 2009)

Hello,
I run 7.1-PRERELEASE, its a home server.
today morning after a power failure, the rebuild my root gm0 failed on disk ad4.
The messages were:

```
May 18 08:02:02 panix kernel: ad4: WARNING - WRITE_DMA UDMA ICRC error (retrying request) LBA=268091264
May 18 08:02:08 panix kernel: drm0: <Intel i865G GMCH> on vgapci0
May 18 08:02:08 panix kernel: info: [drm] AGP at 0xf0000000 128MB
May 18 08:02:08 panix kernel: info: [drm] Initialized i915 1.5.0 20060119
May 18 08:02:08 panix kernel: drm0: [ITHREAD]
May 18 08:02:08 panix kernel: ad4: FAILURE - device detached
May 18 08:02:08 panix kernel: subdisk4: detached
May 18 08:02:08 panix kernel: ad4: detached
May 18 08:02:08 panix kernel: GEOM_MIRROR: Device gm0: provider ad4 disconnected.
May 18 08:02:08 panix kernel: GEOM_MIRROR: Device gm0: rebuilding provider ad4 stopped.
```
I read http://www.eztiger.org/2008/08/removing-and-re-adding-a-disk-in-gmirror/
hoping that the rebuild failure was temporary
and so i tried to just run 

[cmd=]# gmirror forget gm0
# gmirror insert gm0 ad4[/cmd]

But the system responded (if i remember correctly)  

```
Unknown provider ad4.
```
The system no longer could see ad4 being online.

So i rebooted the system many times and had these results:

-When having put offline ad4 (disconnected by hardware), the system booted ok.
-When having both disks online the system responded consistently 
with:

```
GEOM_MIRROR: Cannot add disk ad6 to gm0 (error=22).
```
Which IMO is not very ok, since gm0 should add ad6 without problem,
no matter if ad4 is online or not.
-When having only ad4 online, then it simply cannot find gm0 at all. (kind of reasonable)

So my only option is to have only ad6 online, with a current gmirror status:


```
panix# gmirror status
      Name    Status  Components
mirror/gm0  COMPLETE  ad6
```

Anyone has an idea of how should i proceed (besides buying a UPS unit!)
Is it meaningful to go for a new Disk to replace current ad4?
Why is the presence of the supposed bad disk ad4, affecting gm0,
when having already told gm0 to forget about ad4?

Thanx for any suggestions.


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## SirDice (May 18, 2009)

It does look like the ad4 is dead, so replacing it would be the best option.


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## achix (May 19, 2009)

Thanx, that's what i did, and gm0 rebuilt without issues.


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