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https://issues.apache.org/jira/browse/BOOKKEEPER-432?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13489363#comment-13489363
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Ivan Kelly commented on BOOKKEEPER-432:
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I've posted some results we had benchmarking against hbase's hregion format
which you guys might be interested in.
https://github.com/ivankelly/bkvhbase/wiki/Performance-Graphs
{quote}
The per-ledger index file just holds information which btree-file the entries
are stored. We could just look up the b-tree using its index block and data
blocks, which are all LRU cached
{quote}
So all entries for a single ledger will be stored sequentially on disk in a
single file. Instead of storing, in the index file, which btree file contains
the ledger entries, couldn't you store the file and the offset to the entries?
It would save you having to go to the file index at all.
{quote}
we can enhance HedWig to batch read entries from Bookies.
{quote}
This is something I think the bookkeeper client has needed for quite a while.
> Improve performance of entry log range read per ledger entries
> ---------------------------------------------------------------
>
> Key: BOOKKEEPER-432
> URL: https://issues.apache.org/jira/browse/BOOKKEEPER-432
> Project: Bookkeeper
> Issue Type: Improvement
> Components: bookkeeper-server
> Affects Versions: 4.2.0
> Environment: Linux
> Reporter: Yixue (Andrew) Zhu
> Assignee: Yixue (Andrew) Zhu
> Labels: patch
> Attachments: BookieLedgerStorageProposal.pdf
>
>
> We observed random I/O reads when some subscribers fall behind (on some
> topics), as delivery needs to scan the entry logs (thru ledger index), which
> are interleaved with ledger entries across all ledgers being served.
> Essentially, the ledger index is a non-clustered index. It is not effective
> when a large number of ledger entries need to be served, which tend to be
> scattered around due to interleaving.
> Some possible improvements:
> 1. Change the ledger entries buffer to use a SkipList (or other suitable),
> sorted on (ledger, entry sequence). When the buffer is flushed, the entry log
> is written out in the already-sorted order.
> The "active" ledger index can point to the entries buffer (SkipList), and
> fixed up with entry-log position once latter is persisted.
> Or, the ledger index can be just rebuilt on demand. The entry log file tail
> can have index attached (light-weight b-tree, similar with big-table). We
> need to track per ledger which log files contribute entries to it, so that
> in-memory index can be rebuilt from the tails of corresponding log files.
> 2. Use affinity concept to make ensembles of ledgers (belonging to same
> topic) as identical as possible. This will help above 1. be more effective.
>
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