Thinking of using ZFS/FBSD for a backup system

[Kris Kennaway]

aslam_mohamed at wordbank.com wrote:
> Hi,
> I have been using FreeBSD/ZFS for our backup system for last few 
> months.. We had 6TB external disks connected through Firewire to the 
> Server. Last week all the backup data disappeared along with the pool 
> and everything!!!..When I typed zpool status - it says no pool 
> available..Build up to this incident has always been a firefighting 
> situation for me. We use Rsync to sync all the servers to FreeBSD's ZFS 
> pool everyday. Most of the time Rsync hung on the middle of the syncing 
> process.  When this happen I have to restart the server to run the 
> backup again and  mount the ZFS pool (it requires manual mounting most 
> of the time!!). Sometimes it throws some error like -
> GEOM: da0: corrupt or invalid GPT detected.
> GEOM: da0: GPT rejected -- may not be recoverable.
> GEOM: da1: corrupt or invalid GPT detected.
> GEOM: da1: GPT rejected -- may not be recoverable
> I don't know what caused the disappearance of the ZFS pool and if 
> someone could explain how I can retrieve the data from the external 
> disks, that would be really helpful?..

What you pasted says that the disks were rejected by GEOM because the 
partition table was "corrupt or invalid".  I don't know for sure why 
this might be, but one possible cause would be if there is data 
corruption in your I/O path.  Do you get errors from ZFS about checksum 
failures or other errors?  Maybe there is a problem with the firewire 
stack, or support for your firewire hardware.

The rsync hanging is almost certainly either for the same memory reasons 
we have been discussing, or a side effect of I/O problems to the disks.

Kris