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https://issues.apache.org/jira/browse/HBASE-24?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12613082#action_12613082
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LN commented on HBASE-24:
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from my profiling result, memory usage of a regionserver is determined by 2
things:
1. the mapfile index read into memory(io.map.index.skip can adjust it, buf
allwill stay in mem weather u need it or not)
2. data output buffer used by each SequenceFile$Reader(each can measured as the
largest value size in the file)
3. memcache, can controlled by hbase itsself.
so, when concurrent open mapfiles limited, memory usage of a regionserver
limited too. otherwise, a regionserver will cause OOME when data size
increasing. in my test env, 100G data(200M mapfile index total, 2000
HStoreFiles opened, 512M mamcache) used 1.5G heap memory, the max i can set
using -Xmx.
i think this issue should be seriously concerned by Hbase, not only DFS side.
> Scaling: Too many open file handles to datanodes
> ------------------------------------------------
>
> Key: HBASE-24
> URL: https://issues.apache.org/jira/browse/HBASE-24
> Project: Hadoop HBase
> Issue Type: Bug
> Components: regionserver
> Reporter: stack
> Priority: Critical
>
> 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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