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From Gaojinchao <gaojinc...@huawei.com>
Subject Why writes a meta HRegionInfo for blockcache/InMemory is off to hdfs system?
Date Thu, 05 Jan 2012 11:01:43 GMT
Below code is doing this when we start a cluster.

Code:
private static void bootstrap(final Path rd, final Configuration c)
  throws IOException {
    LOG.info("BOOTSTRAP: creating ROOT and first META regions");
    try {
      // Bootstrapping, make sure blockcache is off.  Else, one will be
      // created here in bootstap and it'll need to be cleaned up.  Better to
      // not make it in first place.  Turn off block caching for bootstrap.
      // Enable after.
      HRegionInfo rootHRI = new HRegionInfo(HRegionInfo.ROOT_REGIONINFO);
      setInfoFamilyCaching(rootHRI, false);
      HRegionInfo metaHRI = new HRegionInfo(HRegionInfo.FIRST_META_REGIONINFO);
      setInfoFamilyCaching(metaHRI, false);
      HRegion root = HRegion.createHRegion(rootHRI, rd, c);
      HRegion meta = HRegion.createHRegion(metaHRI, rd, c);
      setInfoFamilyCaching(rootHRI, true);
      setInfoFamilyCaching(metaHRI, true);

I found “IN_MEMORY => 'false', BLOCKCACHE => 'false'”  in hdfs system.

       .META.,,1.META.[1]IS_ROOTfalseIS_META
________________________________
true
________________________________
info
BLOOMFILTER
________________________________
NONEREPLICATION_SCOPE0
COMPRESSION
________________________________
NONEVERSIONS[1]10
________________________________
TTL
2147483647     BLOCKSIZE
________________________________
8192     IN_MEMORYfalse
BLOCKCACHEfalseK��

REGION => {NAME => '.META.,,1', STARTKEY => '', ENDKEY => '', ENCODED => 1028785192,
TABLE => {{NAME => '.META.', IS_META => 'true', FAMILIES => [{NAME => 'info',
BLOOMFILTER => 'NONE', REPLICATION_SCOPE => '0', COMPRESSION => 'NONE', VERSIONS
=> '10', TTL => '2147483647', BLOCKSIZE => '8192', IN_MEMORY => 'false', BLOCKCACHE
=> 'false'}]}}
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