anchor.diff:  * hbase.regionserver.hlog.blocksize defaults to 2x the HDFS default block size for the WAL dir. Previously it was equal to the HDFS default block size for the WAL dir.
   * hbase.client.start.log.errors.counter changed to 5. Previously it was 9.
   * hbase.ipc.server.callqueue.type changed to 'fifo'. In HBase versions 1.0 - 1.2 it was 'deadline'. In prior and later 1.x versions it already defaults to 'fifo'.
  -* hbase.hregion.memstore.chunkpool.maxsize is 1.0 by default. Previously it was 0.0. Effectively, this means previously we would not use a chunk pool when our memstore is onheap and now we will. See the section <<gcpause>> for more infromation about the MSLAB chunk pool.
  +* hbase.hregion.memstore.chunkpool.maxsize is 1.0 by default. Previously it was 0.0. Effectively, this means previously we would not use a chunk pool when our memstore is onheap and now we will. See the section <<gcpause>> for more information about the MSLAB chunk pool.
   * hbase.master.cleaner.interval is now set to 10 minutes. Previously it was 1 minute.
   * hbase.master.procedure.threads will now default to 1/4 of the number of available CPUs, but not less than 16 threads. Previously it would be number of threads equal to number of CPUs.
   * hbase.hstore.blockingStoreFiles is now 16. Previously it was 10.
  
positive.code: 
  After the Apache HTrace project moved to the Attic/retired, the traces in HBase are left broken and unmaintained since HBase 2.0. A new project link:https://issues.apache.org/jira/browse/HBASE-22120[HBASE-22120] will replace HTrace with OpenTelemetry. It will be shipped in 3.0.0 release. Please see the reference guide section <<tracing>> for more details.
  
  [[upgrade2.0.hfile.compatability]]
  .HFile lose forward compatability
  
  HFiles generated by 2.0.0, 2.0.1, 2.1.0 are not forward compatible to 1.4.6-, 1.3.2.1-, 1.2.6.1-,
  and other inactive releases. Why HFile lose compatability is hbase in new versions
  (2.0.0, 2.0.1, 2.1.0) use protobuf to serialize/deserialize TimeRangeTracker (TRT) while old
  versions use DataInput/DataOutput. To solve this, We have to put
  link:https://jira.apache.org/jira/browse/HBASE-21012[HBASE-21012]
  
negative.code: [[upgrade2.0]]
  === Upgrading from 1.x to 2.x
  
  In this section we will first call out significant changes compared to the prior stable HBase release and then go over the upgrade process. Be sure to read the former with care so you avoid surprises.
  
  ==== Changes of Note!
  
  