[
https://issues.apache.org/jira/browse/HDFS-3023?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13218375#comment-13218375
]
Todd Lipcon commented on HDFS-3023:
-----------------------------------
I do think the log size is the major difference causing the performance issues
in HDFS-3010. In my initial benchmarks last night (which included only one of
the above optimizations) the regression was only 7% vs the ~20% I had seen in
earlier testing. But, these results aren't reliable since I also switched to a
different cluster between benchmarks. I'll rerun the benchmarks today.
Also worth noting - you referred to "option #2 vs option #3" above, but really
option #3 is combined with option #2 for extra savings (ie the OP_UPDATE_BLOCKS
is around half to 1/3 the size because of the delta-vint-encoded genstamps and
sizes)
> Optimize entries in edits log for persistBlocks calls
> -----------------------------------------------------
>
> Key: HDFS-3023
> URL: https://issues.apache.org/jira/browse/HDFS-3023
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: name-node, performance
> Affects Versions: HA branch (HDFS-1623), 0.23.2
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Attachments: hdfs-3023-HDFS-1623.txt
>
>
> One of the performance issues noticed in the HA branch is due to the much
> larger edit logs, now that we are writing OP_ADD transactions to the edit log
> on every block allocation. We can condense these calls down in two ways:
> 1) use variable-length integers for the block list length, size, and genstamp
> (most of these end up fitting in far less than 8 bytes)
> 2) use delta-coding for the genstamp and block size for any blocks after the
> first block (most blocks will be the same size and only slightly higher
> genstamps)
> 3) introduce a new OP_UPDATE_BLOCKS transaction that doesn't re-serialize
> metadata information like lease owner, permissions, etc
> 4) allow OP_UPDATE_BLOCKS to only re-serialize the blocks that have changed
> for a given transaction
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
