Re: HDFS replica management

Phantom wrote:
> Here is the scenario I was concerned about. Consider
three nodes in the
> system A, B and C which are placed say in different
racks. Let us say that
> the disk on A fries up today. Now the blocks that were
stored on A are not
> going to re-replicated (this is my understanding but I
could be wrong in
> this assumption) to some other node or to the new disk
with which you would
> bring back A.

That's incorrect.  When a datanode fails to send a heartbeat
to the 
namenode in a timely manner then its data is assumed missing
and is 
re-replicated.  And when block corruption is detected,
corrupt replicas 
are removed and non-corrupt replicas are re-replicated to
maintain the 
desired level of replication.

Doug

That's awesome.

Thanks
A

On 7/17/07, Doug Cutting <cuttingapache.org> wrote:
>
> Phantom wrote:
> > Here is the scenario I was concerned about.
Consider three nodes in the
> > system A, B and C which are placed say in
different racks. Let us say
> that
> > the disk on A fries up today. Now the blocks that
were stored on A are
> not
> > going to re-replicated (this is my understanding
but I could be wrong in
> > this assumption) to some other node or to the new
disk with which you
> would
> > bring back A.
>
> That's incorrect.  When a datanode fails to send a
heartbeat to the
> namenode in a timely manner then its data is assumed
missing and is
> re-replicated.  And when block corruption is detected,
corrupt replicas
> are removed and non-corrupt replicas are re-replicated
to maintain the
> desired level of replication.
>
> Doug
>