ZFS...

[Borja Marcos]

> On 8 May 2019, at 05:09, Walter Parker <walterp at gmail.com> wrote:
> Would a disk rescue program for ZFS be a good idea? Sure. Should the lack
> of a disk recovery program stop you from using ZFS? No. If you think so, I
> suggest that you have your data integrity priorities in the wrong order
> (focusing on small, rare events rather than the common base case).

ZFS is certainly different from other flesystems. Its self healing capabilities help it survive problems 
that would destroy others. But if you reach a level of damage past that “tolerable” threshold consider
yourself dead.

Is it possible at all to write an effective repair tool? It would be really complicated.

By the way, ddrescue can help in a multiple drive failure scenery with ZFS. If some of the drives are
showing the typical problem of “flaky” sectors with a lot of retries slowing down the whole pool you can
shut down the system or at least export the pool, copy the required drive/s to fresh ones, replace the
flaky drives and try to import the pool. I would first do the experiment to make sure it’s harmless,
but ZFS relies on labels written on the disks to import a pool regardless of disk controller topology,
devices names, uuids, or whatever.  So a full disk copy should work. 

Michelle, were you doing periodic scrubs? I’m not sure you mentioned it. 





Borja.