[jira] [Assigned] (KUDU-1952) round-robin block allocation can place all blocks for a given column on one disk

["Andrew Wong (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KUDU-1952?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andrew Wong reassigned KUDU-1952:
---------------------------------

    Assignee: Andrew Wong

> round-robin block allocation can place all blocks for a given column on one disk
> --------------------------------------------------------------------------------
>
>                 Key: KUDU-1952
>                 URL: https://issues.apache.org/jira/browse/KUDU-1952
>             Project: Kudu
>          Issue Type: Bug
>          Components: fs, perf
>    Affects Versions: 1.3.0
>            Reporter: Todd Lipcon
>            Assignee: Andrew Wong
>
> Currently the LBM allocates across disks in round-robin order. I ran a test using 4 data disks and a table with 12 columns. This caused very uneven allocation across disks, since all data for column N ended up on disk N%4. This also makes single-column scans slow since they read from only a single disk.
> In a more mixed workload this is likely to be less problematic, but still it seems like we should take available space into consideration for allocation, and/or add more randomness.



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