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From Jonathan Hsieh <...@cloudera.com>
Subject [DISCUSSION] Merge of the hbase-11339 mob branch into master.
Date Wed, 20 May 2015 16:21:20 GMT
Hi folks,

The Medium Object (MOB) Storage feature (HBASE-11339[1]) is modified I/O
and compaction path that allows individual moderately sized values
(10k-10MB) to be stored so that write amplification is reduced when
compared to the normal I/O path.   At a high level, it provides alternate
flush and compaction mechanisms that segregates large cells into a separate
area where they are not subject to potentially frequent compaction and
splits that can be encountered in the normal I/O path. A more detailed
design doc can be found on the hbase-11339 jira.

Jingcheng Du has been working on the mob feature for a while and Anoop, Ram
and I have been shepherding him through the design revisions and
implementation of the feature in the hbase-11339 branch.[2]

The branch we are proposing to merge into master is compatible with HBase's
core functionality including snapshots, replication, shell support, behaves
well with table alters, bulk loads and does not require external MR
processes. It has been documented, and subject to many integration test
runs  (ITBLL, ITAcidGuarantees, ITIngest) including fault injection.
Performance testing of the feature shows what can be a 2x-3x throughput
improvement for workloads that contain mobs. These results can be seen on
the hbase 2.0 panel discussion slides from hbasecon (once published).

Recently there have been some hfile encryption related shortcomings that we
could address in branch or in master.

Earlier iterations of the feature has been tested in production by users
that Jingcheng has been responsible for.  A version has also been deployed
at users I have been responsible for.  Some of the folks from Huawei
(ashutosh) have also been submitting the recent encryption bug reports
against the hbase-11339 branch so there is some evidence of usage by them.

The four of us  (Jingcheng, Ram, Anoop and I) are satisfied with the
feature and feel it is a good time to call a merge vote.  Ive posted a
megapatch version for folks who want to peruse the code. [3]

What do you all think?

Jingcheng, Jon, Ram, and Anoop.

[1] https://issues.apache.org/jira/browse/HBASE-11339
[2] https://github.com/apache/hbase/tree/hbase-11339
[3] https://reviews.apache.org/r/34475/
// Jonathan Hsieh (shay)
// HBase Tech Lead, Software Engineer, Cloudera
// jon@cloudera.com // @jmhsieh

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