[Ocfs2-devel] Question: recovery map vs replay map

[Goldwyn Rodrigues]

On Fri, Oct 8, 2010 at 2:50 PM, Sunil Mushran <sunil.mushran at oracle.com> wrote:
> On 10/08/2010 12:03 PM, Goldwyn Rodrigues wrote:
>>
>> I was reading through the recovery code and got confused with recovery
>> and replay maps.
>>
>> What is the function of recovery maps and replay maps? Is a replay map
>> generated for each entry in the recovery map? Is there a situation
>> where a replay map is created without a recovery map entry?
>>
>
> During recovery, we need to recover the slot used by the dead node
> (including journal replay) and clean up the unused orphaned inodes.
>
> The recovery map refers to the nodes whose slot needs recovery.
>
> The replay map (confusing name, in hindsight) refers to unused slots
> whose orphaned inodes need to be cleaned up.
>
> Consider the case of a 4 node cluster having nodes 0, 1, 2, 3.
> Say node 0 removes a file that is in-use on node 1. Node 0 will
> move the inode to its orphan directory. Then say it umounts.
> At this stage, say node 1 dies.
>
> One of the surviving nodes will recover the node 1's slot. That
> includes replaying its journal and cleaning up its orphan directory.
>
> But what about the orphan directory that node 0 used that has that
> inode that was in use on node 1. That needs to be cleaned up too.
>
> The replay map, populated with unused slots, will contain the slot
> used by node 0.


Thanks Sunil. This example clears a lot of doubts.


-- 
Goldwyn