HBase 0.90.0 is the major HBase release to follow HBase-0.20.x and the
fruit of the 0.89.x development release series we've been running over
the last few months.
Over 1k issues have been closed since 0.20.0. Release notes are
available here: http://su.pr/8LbgvK. Highlights include new master,
inter-cluster replication, data durability, improved performance,
improved i/o profile, etc.
We recommend all upgrade to this release but ONLY after a close reading
of requirements . In particular, see the section on Hadoop where we
talk about the Hadoop versions and HBase 0.90.0.
There is no migration necessary. Your data written with HBase 0.20.x
(or with HBase 0.89.x) is readable by HBase 0.90.0. A shutdown and
restart after putting in place the new HBase should be all thats
involved. That said, once done, there is no (easy) going back to 0.20.x once
the transition has been made. HBase 0.90.0 and HBase 0.89.x write
region names differently in the filesystem. Rolling restart from
0.20.x or 0.89.x to 0.90.0RC1 will not work.
A big thanks goes out to all who contributed to this release.
P.S. For why the version 0.90 and whats new in HBase 0.90, see slides
4-10 in this deck, .