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Pavel Yaskevich commented on CASSANDRA-2749:
--------------------------------------------
After crushing my head again this for a few days I can say that this is more
complicated that it sounds for a few reasons:
- We will need to support both old/new directory structures which requires
major changes in the way how Descriptor class works and how CFS and SSTable
classes do file lookup and path generation.
- Adds additional complexity to the way how we do backups, snapshots and
recover which could potentially lead to some nasty bugs.
- As Peter already mentioned "Cassandra won't be able to distinguish between
an actual empty CF and a directory that wasn't mounted (or a symlink pointing
to a non-mounted directory)".
There are more but those mentioned are major ones. Let's skip this for now.
> 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
> Assignee: Pavel Yaskevich
> Priority: Minor
>
> 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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