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From Hannu Kröger (JIRA) <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-12907) Different data directories for SSDs and HDDs at configuration level
Date Tue, 29 Aug 2017 13:29:01 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-12907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16145285#comment-16145285
] 

Hannu Kröger commented on CASSANDRA-12907:
------------------------------------------

One idea would be also to extract the file placing logic to a different extensible class which
could be then replaced by configurable plugin like "SSDMetadataFilePlacingStrategy" with parameter
"ssd_directory_locations". Then it would be possible to implement both: one strategy to store
only metadata and indexes on ssds and another to store certain tables fully in different location".

When opening files, all locations probably should be checked for easy migration from one approach
to another.

> Different data directories for SSDs and HDDs at configuration level
> -------------------------------------------------------------------
>
>                 Key: CASSANDRA-12907
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12907
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Natale Galioto
>              Labels: performance
>
> Currently, users can speed up some CFs by symlinking its data directory to fast media
such as SSDs. In my opinion, instead, configuration file should allow two different sets of
directory: one dedicated to spindles, one dedicated to SSDs. 
> This would allow a "once and for all mixed SSD & HDD configuration", instead of continuously
symlinking the "right" directory each time a CF is created (due to the name mangling of the
CF directories).
> And this in turn would allow a priori knowledge on disk structures, and would allow to
place indexes of all sort (lookup, partition, etc... everything that is needed to "just" locate
data) on fast SSDs, speeding up ALL the CFs instead of only one, while the HDDs could be used
just for data retrieval and sequential reads. 



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