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From "Marcus Eriksson (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2749) fine-grained control over data directories
Date Tue, 06 Dec 2011 12:57:41 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2749?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13163570#comment-13163570
] 

Marcus Eriksson commented on CASSANDRA-2749:
--------------------------------------------

agree that the file structure is all over the place, that's why this patch was so incredibly
painful to do

seems i only did the disk space checking in sub directories in the backwards compatible patch

i had on algorithm for detecting what kind of file it is in the old backwards compatible patch,
it iterates over all data directories and figures out which data directory the file is in,
then it knows the keyspace is the next part of the filename, and can check if there are files
or directories in that directory.

but i agree, it is incredibly ugly, your modifications make it alot better, and yes, this
would be a good time to do this properly, not like me just trying to do a minimal patch that
"works".

regarding keyspaces in file names, sure, why not, guess having a header with this info in
the file is out of the question, then the only meta data we have is the file name, right?
A problem could be if we want to do CASSANDRA-1983 later, that would increase the file name
length even more.
                
> fine-grained control over data directories
> ------------------------------------------
>
>                 Key: CASSANDRA-2749
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2749
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Jonathan Ellis
>            Priority: Minor
>             Fix For: 1.1
>
>         Attachments: 0001-Make-it-possible-to-put-column-families-in-subdirect.patch,
0001-add-new-directory-layout.patch, 0001-non-backwards-compatible-patch-for-2749-putting-cfs-.patch.gz,
0002-fix-unit-tests.patch, 2749.tar.gz, 2749_backwards_compatible_v1.patch, 2749_backwards_compatible_v2.patch,
2749_backwards_compatible_v3.patch, 2749_backwards_compatible_v4.patch, 2749_backwards_compatible_v4_rebase1.patch,
2749_not_backwards.tar.gz, 2749_proper.tar.gz
>
>
> Currently Cassandra supports multiple data directories but no way to control what sstables
are placed where. Particularly for systems with mixed SSDs and rotational disks, it would
be nice to pin frequently accessed columnfamilies to the SSDs.
> Postgresql does this with tablespaces (http://www.postgresql.org/docs/9.0/static/manage-ag-tablespaces.html)
but we should probably avoid using that name because of confusing similarity to "keyspaces."

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