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https://issues.apache.org/jira/browse/HBASE-24?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13089042#comment-13089042
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Alex Newman commented on HBASE-24:
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+            conf); // defer opening streams
is in the patch. Are we actually still defering. That seems wrong.

> Scaling: Too many open file handles to datanodes
> ------------------------------------------------
>
>                 Key: HBASE-24
>                 URL: https://issues.apache.org/jira/browse/HBASE-24
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>            Reporter: stack
>            Priority: Blocker
>         Attachments: HBASE-823.patch, MonitoredReader.java
>
>
> We've been here before (HADOOP-2341).
> Today the rapleaf gave me an lsof listing from a regionserver.  Had thousands 
> of open sockets to datanodes all in ESTABLISHED and CLOSE_WAIT state.  On 
> average they seem to have about ten file descriptors/sockets open per region 
> (They have 3 column families IIRC.  Per family, can have between 1-5 or so 
> mapfiles open per family -- 3 is max... but compacting we open a new one, 
> etc.).
> They have thousands of regions.   400 regions -- ~100G, which is not that 
> much -- takes about 4k open file handles.
> If they want a regionserver to server a decent disk worths -- 300-400G -- 
> then thats maybe 1600 regions... 16k file handles.  If more than just 3 
> column families..... then we are in danger of blowing out limits if they are 
> 32k.
> We've been here before with HADOOP-2341.
> A dfsclient that used non-blocking i/o would help applications like hbase 
> (The datanode doesn't have this problem as bad -- CLOSE_WAIT on regionserver 
> side, the bulk of the open fds in the rapleaf log, don't have a corresponding 
> open resource on datanode end).
> Could also just open mapfiles as needed, but that'd kill our random read 
> performance and its bad enough already.

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