panic: ffs_valloc: dup alloc

[Eric Anderson]

Uwe Doering wrote:
> Eric Anderson wrote:
>> I get the above panic after nfs clients attach to this nfs server and 
>> being read/write ops on it after an unclean shutdown.  I've fsck'ed 
>> the fs, and it marks it as clean, but I get this every time.  It's an 
>> NFS share of a GEOM stripe (about 2TB).
>> mode = 0100600, inum = 58456203, fs = /mnt
>> panic: ffs_valloc: dup alloc
>
> Do you happen to have disk mirroring on this server (RAID 1)?  At 
> work, on a workstation with RAID 1, we once had a case where after a 
> power failure fsck would succeed, but subsequently, when mounting and 
> using the partitions, the kernel still paniced because of a corrupt 
> filesystem.  Repeatedly.
>
> This caused some major head scratching on our part until we figured 
> out what was happening.  The mirrored disks had gone out of sync.  For 
> performance reasons, a RAID 1 controller reads data from one disk 
> drive or the other, depending on which drive is less busy in that 
> particular moment.  So while fsck was able to find and fix some 
> filesystem inconsistencies there were still some more left in disk 
> sectors it didn't access.
>
> The RAID controller we used turned out to have a verification mode 
> where it would scan the disks and re-synchronize them.  Afterwards we 
> did another fsck run, and this fixed the remaining filesystem 
> inconsistencies.  The kernel panics were gone.
>
> Now, with the information you've provided I can't tell whether these 
> findings apply to your case, but perhaps this story helps at least 
> others in a similar situation.

I do have mirroring enabled on the OS drives, but this is happening with 
an external fiber channel array of SATA disks, striped using gstripe. 

Eric



-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
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