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From Saad Mufti <saad.mu...@gmail.com>
Subject Slow sync cost
Date Mon, 25 Apr 2016 19:18:55 GMT
Hi,

In our large HBase cluster based on CDH 5.5 in AWS, we're constantly seeing
the following messages in the region server logs:

2016-04-25 14:02:55,178 INFO
org.apache.hadoop.hbase.regionserver.wal.FSHLog: Slow sync cost: 258 ms,
current pipeline:
[DatanodeInfoWithStorage[10.99.182.165:50010,DS-281d4c4f-23bd-4541-bedb-946e57a0f0fd,DISK],
DatanodeInfoWithStorage[10.99.182.236:50010,DS-f8e7e8c9-6fa0-446d-a6e5-122ab35b6f7c,DISK],
DatanodeInfoWithStorage[10.99.182.195:50010
,DS-3beae344-5a4a-4759-ad79-a61beabcc09d,DISK]]


These happen regularly while HBase appear to be operating normally with
decent read and write performance. We do have occasional performance
problems when regions are auto-splitting, and at first I thought this was
related but now I se it happens all the time.


Can someone explain what this means really and should we be concerned? I
tracked down the source code that outputs it in

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/FSHLog.java

but after going through the code I think I'd need to know much more about
the code to glean anything from it or the associated JIRA ticket
https://issues.apache.org/jira/browse/HBASE-11240.

Also, what is this "pipeline" the ticket and code talks about?

Thanks in advance for any information and/or clarification anyone can
provide.

----

Saad

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