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https://issues.apache.org/jira/browse/KUDU-1755?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Grant Henke reopened KUDU-1755:
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> Improve tablet disk space estimation
> ------------------------------------
>
> Key: KUDU-1755
> URL: https://issues.apache.org/jira/browse/KUDU-1755
> Project: Kudu
> Issue Type: Bug
> Components: supportability, tablet
> Affects Versions: 1.1.0
> Reporter: Adar Dembo
> Assignee: Grant Henke
> Priority: Critical
> Fix For: 1.3.0
>
>
> (Prompted by [this user
> post|http://mail-archives.apache.org/mod_mbox/kudu-user/201611.mbox/%3Ctencent_201BBF963FB5CB2D7AF99E25%40qq.com%3E])
> The on-disk size of tablets as reported by the Kudu web UI omits some minor
> as well as some major sources of space consumption. I'm listing them all here
> for posterity.
> # Bloom file and composite index file usage. According to [this
> gerrit|https://gerrit.sjc.cloudera.com/#/c/6070/] (warning: internal link),
> it's because we also use the rowset estimate to determine how much IO will be
> generated were we to compact that rowset, and bloom/composite index files
> aren't touched in compaction.
> # UNDO file usage. This seems like a more glaring omission, especially for
> mutation-heavy workloads like the one reported in the mailing list. But, the
> current REDO-only estimate factors into major delta compaction decision
> making by the maintenance manager, so maybe there's a good reason there too.
> # Log block manager block size rounding. The LBM rounds up Kudu blocks to the
> nearest filesystem block size to improve hole punching space reclamation. A
> side effect is that some space is lost to external fragmentation.
> # Log block manager metadata overhead. Every container has a .metadata file,
> and we don't factor that into space utilization.
> # Other files, such as the tablet superblock, WAL segments, and cmeta.
> I expect the first two items to be the largest, so we should work on
> addressing them. Lets decouple the UI-based estimate from the MM path so our
> reporting can be more accurate while still allowing the MM to make good
> decisions.
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