[OpenIndiana-discuss] HBA failover

[Sebastian Gabler]

Dear Bill, Peter, Richard, and Saso.

Thanks for the great comments.

Now, changing to reverse gear, isn't it more likely to loose data by 
having a pool that spans across mutiple HBAs than if you connect all 
drives to a single HBA? I mean, unless you make sure that there are 
never any more drives served by one HBA alone (single-ported SATA 
drives) in a leaf VDEV than can be tolerated by the provided redundancy, 
a VDEV in the pool could become unavailable upon HBA failure, ultimately 
leading to loss of the whole pool? That is, given that the failure of 
the HBA would not lead to an immediate crash of the host which would 
make it identical to the previous scenario. I'd claim that such failures 
are probably not handled, and so the consequences are not predictable.
Similar scenarios are feasible if one disk shelf dies completely, and 
the pool spans across more than one.
I have personally seen a single vdev in a pool to go down by drive 
incompatibility, and when I had to decide to give up the pool or try 
recovery, I got the impression from iostat that there probably had been 
transactions to the remaining VDEVs, making the recovery forensics. Not 
sure if this was indeed accurate, but then I was jumping to the 
conclusion that an immediate, hard crash would have been preferable over 
a slow melt-down. Prejudice or fact?


Best regards,

Sebastian