[Drbd-dev] DRBD-8: Update to handle I/O failures during resync

[Philipp Reisner]

Am Montag, 9. Oktober 2006 20:05 schrieb Graham, Simon:

Hi Simon,

Apart from a little whitespace change to make it to conform to
Linus' Linux coding style. I applied the patch as you sent it.

I read through it, and I could not spot anything wrong...

> 1. New fields are added to the mdev and bm_extent structs to count the
>    number of failed requests during resync - the field in bm_extent is
>    used to determine when we are finished with the extent at which
>    time it is zeroed so that next time we process the same extent,
>    we'll try to resync everything again.
>
> 2. Resync is considered done when the remaining count of block to sync
>    is <= the count of failed requests.
>
> 3. When a failure occurs, a new routine, drbd_rs_failed_io() is called
>    to handle this - it takes care of incrementing the failed counts
>    and determining if the resync operation is now done. This is called
>    when a NegRSDreply is sent or received and also when a NegAck is
>    received for a resync operation (this is necessary to ensure that
>    the SyncSource correctly knows when the resync is done).
>
> 4. When a resync operation completes and there have been failure, the
>    new code does NOT rotate the UUIDs - I felt this was correct
>    because the resync really hasn't completed in this case (also, I
>    found that if I did not do this, the code would end up resyncing
>    the entire disk next time!)
>
> I did not introduce any new states for this - let me know if you think
> there needs
> to be one; with this patch, we simply end up Connected and Inconsistent.
>

Right. I will test it here in my environment as well. What more and more
gets obvious that we need a method to start resync without setting the 
bitmap, only to resync what is currently set.

Maybe "drbdadm resync".

Right now I do not see a reason for more states...

Thanks or the patch, great work!

-Philipp
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