[sheepdog] [PATCH v3] sheep/recovery: multi-threading recovery process

[Liu Yuan]

On Tue, Feb 04, 2014 at 03:14:44PM +0800, Liu Yuan wrote:
> Rationale for multi-threaded recovery:
> 
> 1. If one node is added, we find that all the VMs on other nodes will get
>    noticeably affected until 50% data is transferred to the new node.
> 
> 2. For node failure, we might not have problems of running VM but the
>    recovery process boost will benefit IO operation of VM with less
>    chances to be blocked for write and also improve reliability.
> 
> 3. For disk failure in node, this is similar to adding a node. All
>    the data on the broken disk will be recovered on other disks in
>    this node. Speedy recoery not only improve data reliability but
>    also cause less writing blocking on the lost data.
> 
> Our oid scheduling algorithm is intact and simply add multi-threading onto top
> of current recovery algorithm with minimal changes.
> 
> - we still have ->oids array to denote oids to be recovered
> - we start up 2 * nr_disks threads for recovery
> - the tricky part is that we need to wait all the running threads to
>   completion before start next recovery events for multiple nodes/disks events
> 
> This patch passes "./check -g md -md" on my local box
> 

Hitoshi, can this one pass your test 033?

Thanks
Yuan