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From "Yu Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17507) Add document for the mvcc preassign feature introduced in HBASE-16698
Date Sun, 22 Jan 2017 10:43:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17507?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15833446#comment-15833446

Yu Li commented on HBASE-17507:

bq. Yes, A switch can be added, but will increase the complicity of the patch. WAL is not
only appended in put/delete/Append/Increment, but also when writing open/close/compaction/flush
The mvcc preassign feature introduced a per-region level lock, and this is some additional
cost for RS with few regions or cluster with light workload. And as I mentioned, we also observed
some limitations in other case. I'm glad that the design is well recognized, but I'd say be
cautious to make it non-configurable. [~allan163]

bq. Have you compared with multiwal?
Yes, in our online product cluster we're using 4 wals. With more wals could lower the contention
caused by CountDownLatch, but still cannot resolve our problem, which forced us to make this
fix. [~Apache9]

P.S. I'm wondering why the "Reply" function is removed from JIRA, I think "Reply" makes discussion
looks more compacted... [~stack] [~busbey]

> Add document for the mvcc preassign feature introduced in HBASE-16698
> ---------------------------------------------------------------------
>                 Key: HBASE-17507
>                 URL: https://issues.apache.org/jira/browse/HBASE-17507
>             Project: HBase
>          Issue Type: Task
>            Reporter: Yu Li
>            Assignee: Yu Li
> In this JIRA we will supply a design doc of the mvcc preassign mechanism introduced in
HBASE-16698, as well as more detailed performance data of it for better reference.

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