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From "Elliott Clark (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13170) Allow block cache to be external
Date Sat, 07 Mar 2015 07:46:38 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13170?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14351470#comment-14351470
] 

Elliott Clark commented on HBASE-13170:
---------------------------------------

Yes SSD's allow you to persist block cache between restarts. However that's not actually that
helpful for some of my services.

The current bucket cache does not allow two or more regionservers to share the same cache.Moving
single regions for rolling restart can roll them to a full block cache.  I can re-deploy at
any time and the rolling restart only adds the latency of close/open region. It doesn't add
the latency of a cold block cache.

 Read replicas can warm and share each other's cache. No need for double the memory just because
there is a read replica.

Additionally memcached is faster than the cheap ssd's and memory will last for many many more
write cycles. No need to worry about wear leveling, or SSD garbage collection, erasure pages,
etc.

Finally memcache allows scaling the read caching of a HBase cluster independent of expensive
storage nodes.

> Allow block cache to be external
> --------------------------------
>
>                 Key: HBASE-13170
>                 URL: https://issues.apache.org/jira/browse/HBASE-13170
>             Project: HBase
>          Issue Type: New Feature
>          Components: io
>    Affects Versions: 2.0.0
>            Reporter: Elliott Clark
>            Assignee: Elliott Clark
>             Fix For: 1.1.0
>
>
> Allow an external service to provide the block cache. This has the nice property of allowing
failover/upgrades to happen without causing a fully cold cache.
> Additionally this allows read replicas to share some of the same memory.



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