I’ve started HDFS balancer, but then stopped it immediately after knowing that 
it is not a good idea.
but it was around 3 weeks ago, is it possible that it had an influence on the 
cluster behaviour I’m having now?
Thanks.

> On 03 Sep 2015, at 14:23, Akmal Abbasov <[email protected]> wrote:
> 
> Hi Ted,
> No there is no short-circuit read configured.
> The logs of datanode of the 10.10.8.55 are full of following messages
> 2015-09-03 12:03:56,324 INFO 
> org.apache.hadoop.hdfs.server.datanode.DataNode.clienttrace: src: 
> /10.10.8.55:50010, dest: /10.10.8.53:58622, bytes: 77, op: HDFS_READ, cliID: 
> DFSClient_NONMAPREDUCE_-483065515_1, offset: 0, srvID: 
> ee7d0634-89a3-4ada-a8ad-7848214397be, blockid: 
> BP-439084760-10.32.0.180-1387281790961:blk_1075349331_1612273, duration: 
> 276448307
> 2015-09-03 12:03:56,494 INFO 
> org.apache.hadoop.hdfs.server.datanode.DataNode.clienttrace: src: 
> /10.10.8.55:50010, dest: /10.10.8.53:58622, bytes: 538, op: HDFS_READ, cliID: 
> DFSClient_NONMAPREDUCE_-483065515_1, offset: 0, srvID: 
> ee7d0634-89a3-4ada-a8ad-7848214397be, blockid: 
> BP-439084760-10.32.0.180-1387281790961:blk_1075349334_1612276, duration: 
> 60550244
> 2015-09-03 12:03:59,561 INFO 
> org.apache.hadoop.hdfs.server.datanode.DataNode.clienttrace: src: 
> /10.10.8.55:50010, dest: /10.10.8.53:58622, bytes: 455, op: HDFS_READ, cliID: 
> DFSClient_NONMAPREDUCE_-483065515_1, offset: 0, srvID: 
> ee7d0634-89a3-4ada-a8ad-7848214397be, blockid: 
> BP-439084760-10.32.0.180-1387281790961:blk_1075351814_1614757, duration: 
> 755613819
> There are >100.000 of them just for today. The situation with other 
> regionservers are similar.
> Node 10.10.8.53 is hbase-master node, and the process on the port is also 
> hbase-master.
> So if there is no load on the cluster, why there are so much IO happening?
> Any thoughts.
> Thanks.
> 
>> On 02 Sep 2015, at 21:57, Ted Yu <[email protected] 
>> <mailto:[email protected]>> wrote:
>> 
>> I assume you have enabled short-circuit read.
>> 
>> Can you capture region server stack trace(s) and pastebin them ?
>> 
>> Thanks
>> 
>> On Wed, Sep 2, 2015 at 12:11 PM, Akmal Abbasov <[email protected] 
>> <mailto:[email protected]>> wrote:
>> Hi Ted,
>> I’ve checked the time when addresses were changed, and this strange 
>> behaviour started weeks before it.
>> 
>> yes, 10.10.8.55 is region server and 10.10.8.54 is a hbase master.
>> any thoughts?
>> 
>> Thanks
>> 
>>> On 02 Sep 2015, at 18:45, Ted Yu <[email protected] 
>>> <mailto:[email protected]>> wrote:
>>> 
>>> bq. change the ip addresses of the cluster nodes
>>> 
>>> Did this happen recently ? If high iowait was observed after the change 
>>> (you can look at ganglia graph), there is a chance that the change was 
>>> related.
>>> 
>>> BTW I assume 10.10.8.55 <http://10.10.8.55:50010/> is where your region 
>>> server resides.
>>> 
>>> Cheers
>>> 
>>> On Wed, Sep 2, 2015 at 9:39 AM, Akmal Abbasov <[email protected] 
>>> <mailto:[email protected]>> wrote:
>>> Hi Ted,
>>> sorry forget to mention
>>> 
>>>> release of hbase / hadoop you're using
>>> 
>>> hbase hbase-0.98.7-hadoop2, hadoop hadoop-2.5.1
>>> 
>>>> were region servers doing compaction ?
>>> 
>>> I’ve run major compactions manually earlier today, but it seems that they 
>>> already completed, looking at the compactionQueueSize.
>>> 
>>>> have you checked region server logs ?
>>> The logs of datanode is full of this kind of messages
>>> 2015-09-02 16:37:06,950 INFO 
>>> org.apache.hadoop.hdfs.server.datanode.DataNode.clienttrace: src: 
>>> /10.10.8.55:50010 <http://10.10.8.55:50010/>, dest: /10.10.8.54:32959 
>>> <http://10.10.8.54:32959/>, bytes: 19673, op: HDFS_READ, cliID: 
>>> DFSClient_NONMAPREDUCE_1225374853_1, offset: 0, srvID: 
>>> ee7d0634-89a3-4ada-a8ad-7848217327be, blockid: 
>>> BP-329084760-10.32.0.180-1387281790961:blk_1075277914_1540222, duration: 
>>> 7881815
>>> 
>>> p.s. we had to change the ip addresses of the cluster nodes, is it relevant?
>>> 
>>> Thanks.
>>> 
>>>> On 02 Sep 2015, at 18:20, Ted Yu <[email protected] 
>>>> <mailto:[email protected]>> wrote:
>>>> 
>>>> Please provide some more information:
>>>> 
>>>> release of hbase / hadoop you're using
>>>> were region servers doing compaction ?
>>>> have you checked region server logs ?
>>>> 
>>>> Thanks
>>>> 
>>>> On Wed, Sep 2, 2015 at 9:11 AM, Akmal Abbasov <[email protected] 
>>>> <mailto:[email protected]>> wrote:
>>>> Hi,
>>>> I’m having strange behaviour in hbase cluster. It is almost idle, only <5 
>>>> puts and gets.
>>>> But the data in hdfs is increasing, and region servers have very high 
>>>> iowait(>100, in 2 core CPU).
>>>> iotop shows that datanode process is reading and writing all the time.
>>>> Any suggestions?
>>>> 
>>>> Thanks.
>>>> 
>>> 
>>> 
>> 
>> 
> 

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