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https://issues.apache.org/jira/browse/CASSANDRA-8460?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16414748#comment-16414748
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Jon Haddad commented on CASSANDRA-8460:
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{quote}
Thinking some more about this I think the other (and perhaps most important)
advantage of implementing in Cassandra is predictability for operators. It's
easy to say, for example, if I want data < 1 month old to be fast 1 need enough
fast disk space for that and I know it will be consistently fast after that I
need X disk space for the older data and I know it will be slower (and can even
clearly tell users that). Trying to tune performance of the hot data (and avoid
latency spikes) with with Cassandra + LVM sounds pretty hard.
{quote}
I don't see how having Cassandra manage this makes this easier. With LVM you
just set up the cache, and it keeps as much hot data in the cache as it can.
Maybe you only want need a month's worth of data on your hot drive. If you
can't fit a month, lvm cache will manage that just fine because it's a cache
for hot blocks. If you can fit 6 months on the cache, it'll do that fine too.
There isn't any need for configuration, it's literally designed to handle hot
data and you don't need to guess when to tier data off to your cold storage
layer.
> Make it possible to move non-compacting sstables to slow/big storage in DTCS
> ----------------------------------------------------------------------------
>
> Key: CASSANDRA-8460
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8460
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Marcus Eriksson
> Assignee: Lerh Chuan Low
> Priority: Major
> Labels: doc-impacting, dtcs
> Fix For: 4.x
>
>
> It would be nice if we could configure DTCS to have a set of extra data
> directories where we move the sstables once they are older than
> max_sstable_age_days.
> This would enable users to have a quick, small SSD for hot, new data, and big
> spinning disks for data that is rarely read and never compacted.
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