yes. datanode write is pipeline. and only if pipeline writing finished, dn
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On Jun 11, 2013 8:27 AM, "Lucas Stanley" <[EMAIL PROTECTED]> wrote:
> In the Strata 2013 training lectures, Jonathan Hsieh from Cloudera said
> something about HBase syncs which I'm trying to understand further.
> He said that HBase sync guarantees only that a write goes to the local disk
> on the region server responsible for that region and in-memory copies go on
> 2 other machines in the HBase cluster.
> But I thought that when the write goes to the WAL on the first region
> server, that the HDFS append would push that write to 3 machines total in
> the HDFS cluster. In order for the append write to the WAL to be
> successful, doesn't the DataNode on that machine have to pipeline the write
> to 2 other DataNodes?
> I'm not sure what Jonathan was referring to when he said that 2 in-memory
> copies go to other HBase machines? Even when the memstore on the first
> region server gets full, doesn't the flush to the HFile get written on 3
> HDFS nodes in total?