[
https://issues.apache.org/jira/browse/HDFS-1108?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13084511#comment-13084511
]
Todd Lipcon commented on HDFS-1108:
-----------------------------------
bq. We have to log sync after every allocation right, or do you mean only when
HA is enabled? We could consider batching syncs at the cost of response latency
Syncs are already somewhat batched inside of FSEditLog, but it does make the
RPC take longer, holds up the thread, etc. We currently log addBlocks but don't
call logSync, assumedly to save on performance. But, it's at the expense of
correctness, which I think is a mistake. I'll add logSync for now, and if
people find a regression we can add a config to disable it.
bq. Piggy backing the initial allocation on the create makes a lot of sense
agree, let's do that separately
bq. to why DNs are deleting blocks that it currently thinks are part of the
file
abandonBlock happens if the pipeline fails to be established at all, so the DNs
never even get the blocks. So, it's only to prevent a followup addBlock from
adding on top. But I think you're right that it has to log it as well... at the
worst, there's no harm in it.
> Log newly allocated blocks
> --------------------------
>
> Key: HDFS-1108
> URL: https://issues.apache.org/jira/browse/HDFS-1108
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: name-node
> Reporter: dhruba borthakur
> Assignee: Todd Lipcon
> Fix For: HA branch (HDFS-1623)
>
> Attachments: HDFS-1108.patch, hdfs-1108-habranch.txt
>
>
> The current HDFS design says that newly allocated blocks for a file are not
> persisted in the NN transaction log when the block is allocated. Instead, a
> hflush() or a close() on the file persists the blocks into the transaction
> log. It would be nice if we can immediately persist newly allocated blocks
> (as soon as they are allocated) for specific files.
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira
