Re: [Gluster-devel] Glusterd: A New Hope

[Anand Babu Periasamy]

On Tue, Mar 26, 2013 at 8:19 AM, Joe Julian <address@hidden> wrote:
>
>
> Anand Babu Periasamy <address@hidden> wrote:
>
>>On Tue, Mar 26, 2013 at 5:59 AM, Jeff Darcy <address@hidden> wrote:
>>> On 03/25/2013 11:59 PM, Anand Babu Periasamy wrote:
>>>> gluster meta-volume + zeromq for notification (pub/sub) will solve
>>our
>>>> problems largely and still be light weight.  In a large scale
>>>> deployment, it is not a good idea to declare all the servers as
>>>> coordination servers. Since meta-volume is a regular distributed
>>>> replicated gluster volume, it can always be expanded later depending
>>>> on the load and availability requirements.
>>>
>>> How do you propose to solve the bootstrap problem?  How do we choose
>>> which subset of all servers would have pieces of this meta-volume?
>>> How do we coordinate its expansion, or detect and respond to failures
>>of
>>> itscomponents?
>>
>>Admin declares the config servers manually. Automatic option is a
>>disaster waiting to happen.
>>
>>We should set the minimum number of config servers required by default
>>to 3, so that we can enforce quorum. Any failure would require the
>>admin to declare replacement config servers manually.
>
> On that note, the additional quorum functionality should be implemented with 
> regard to watchers before using a glusterfs store for configuration 
> coordination.
>
> From what I've been reading, the biggest thing zookeeper has over any other 
> solution is its robustness with regard to split-brain. If that was managed it 
> seems like that would open up a number of possibilities to satisfy the other 
> requirements.
>

Exactly. Even ZooKeeper requires min 3 servers and odd number of
servers there after. For example of you have 4 servers, it will still
handle only one node failure. With 2 node failures, it cannot elect
majority. Where ever we go, we will have similar issues. We need to
solve these issues for our sync-replication in any case.

-- 
-ab

Imagination is more important than knowledge --Albert Einstein