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From Mikael Sitruk <mikael.sit...@gmail.com>
Subject Re: ANN: The third hbase 0.94.0 release candidate is available for download
Date Sat, 12 May 2012 17:14:12 GMT
Thanks for the clarifications St.Ack.
Still I have some questions in regards of 3 in scenario discussed -  when a
region is offline it means that client operation are not possible on it
(even read)?
In case a second master is up (in an environment with multiple master), i
presume all this occurs unless the second master (slave) become the master,
right? how long those it take for a "slave" master to become a master??

Mikael.S

On Sat, May 12, 2012 at 8:02 AM, Stack <stack@duboce.net> wrote:

> On Fri, May 11, 2012 at 3:24 AM, Mikael Sitruk <mikael.sitruk@gmail.com>
> wrote:
> > Sorry for not being precise enough.
> > The point is that i'm trying to check the impact of HA scenarios. one of
> > them is when the master goes down.
> > That is true that the Master is not it the critical path of read/write
> > unless (please correct me if i'm wrong):
> > 1. new client are trying to connect
>
> Clients don't go to the master, not unless they are trying to do
> administrative ops.
>
> > 2. split/merge occurs
> > 3. another node fails.
>
> If master is down, these events are not processed.  On reboot of
> master, it'll finish the processing of these event types.
>
>
> > So in case the master goes down and start back, i'm interested to
> > understand how long of unavailability the system will be (under the
> > scenario above)
> >
>
> For 2. from above, splits shouldn't cause off-line'd-ness (excuse the
> neologism). The regionserver edits .META. on split offlining parent
> and onlining the split daughters.  It only bothers to tell the master
> about the splits so master can keep current the state of the cluster
> it keeps in its 'head' (when new master comes online, first thing it
> does is reconstitute this image).
>
> For item 3. above, its the master that runs the distributed log split.
>  If no master, no one to run the split so those regions will be
> offline until a master comes online again, finds the offine server and
> runs a spit of its logs.
>
> St.Ack
>

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