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https://issues.apache.org/jira/browse/HBASE-5699?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13293853#comment-13293853
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Todd Lipcon commented on HBASE-5699:
------------------------------------

bq. I think we should wait for test result with HBASE-6116 before we invest 
more time in this.

HBASE-6116 seems like it would improve latency but hurt throughput -- on a 
typical gbit link, the parallel writes would limit us to 50M/sec for 3 
replicas, whereas pipelined writes could give us 100M+.

The other main advantage of this JIRA is that the speed of the WAL is currently 
limited to the minimum speed of the 3 disks chosen in the pipeline. Given that 
disks can be heavily loaded, the probability of getting even a full disk's 
worth of throughput is low -- the likelihood is that at least one of those 
disks is also being written to or read from at least another client. So 
typically any single HDFS stream is limited to 35-40MB/sec in my experience.

Given that gbit is much faster than this, we can get better throughput by 
adding parallel WALs, so as to stripe across disks and dynamically push writes 
to less-loaded disks.
                
> Run with > 1 WAL in HRegionServer
> ---------------------------------
>
>                 Key: HBASE-5699
>                 URL: https://issues.apache.org/jira/browse/HBASE-5699
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: binlijin
>            Assignee: Li Pi
>         Attachments: PerfHbase.txt
>
>


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