hadoop2.2.0 core-site.xml--i/o properties

<!-- i/o properties -->

<property>  <name>io.file.buffer.size</name>  <value>4096</value>  <description>The size of buffer for use in sequence files.  The size of this buffer should probably be a multiple of hardware  page size (4096 on Intel x86), and it determines how much data is  buffered during read and write operations.</description></property>

注释：操作sequence文件时的缓存大小。

<property>  <name>io.bytes.per.checksum</name>  <value>512</value>  <description>The number of bytes per checksum.  Must not be larger than  io.file.buffer.size.</description></property>

注释：

<property>  <name>io.skip.checksum.errors</name>  <value>false</value>  <description>If true, when a checksum error is encountered while  reading a sequence file, entries are skipped, instead of throwing an  exception.</description></property>

注释：

<property>  <name>io.compression.codecs</name>  <value>org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec,org.apache.hadoop.io.compress.DeflateCodec,org.apache.hadoop.io.compress.SnappyCodec,org.apache.hadoop.io.compress.Lz4Codec</value>  <description>A list of the compression codec classes that can be used                for compression/decompression.</description></property>

注释：

<property>  <name>io.serializations</name>  <value>org.apache.hadoop.io.serializer.WritableSerialization,org.apache.hadoop.io.serializer.avro.AvroSpecificSerialization,org.apache.hadoop.io.serializer.avro.AvroReflectSerialization</value>  <description>A list of serialization classes that can be used for  obtaining serializers and deserializers.</description></property>

注释：

<property>  <name>io.seqfile.local.dir</name>  <value>${hadoop.tmp.dir}/io/local</value>  <description>The local directory where sequence file stores intermediate  data files during merge.  May be a comma-separated list of  directories on different devices in order to spread disk i/o.  Directories that do not exist are ignored.  </description></property>

注释：

<property>  <name>io.map.index.skip</name>  <value>0</value>  <description>Number of index entries to skip between each entry.  Zero by default. Setting this to values larger than zero can  facilitate opening large MapFiles using less memory.</description></property>

注释：

property>  <name>io.map.index.interval</name>  <value>128</value>  <description>    MapFile consist of two files - data file (tuples) and index file    (keys). For every io.map.index.interval records written in the    data file, an entry (record-key, data-file-position) is written    in the index file. This is to allow for doing binary search later    within the index file to look up records by their keys and get their    closest positions in the data file.  </description></property>

注释：