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From Casey Deccio <ca...@deccio.net>
Subject Disk configuration in new cluster node
Date Fri, 14 Sep 2012 19:39:34 GMT
I'm building a new "cluster" (to replace the broken setup I've written
about in previous posts) that will consist of only two nodes.  I understand
that I'll be sacrificing high availability of writes if one of the nodes
goes down, and I'm okay with that.  I'm more interested in maintaining high
consistency and high read availability.  So I've decided to use a
write-level consistency of ALL and read-level consistency of ONE.

My first question is about the drives in this setup.  If I initially set up
the system with, say, 4 drives for data and 1 drive for commitlog, and
later I decide to add more capacity to the node by adding more drives for
data (adding the new data directory entries in cassandra.yaml), will the
node balance out the load on the drives, or is it agnostic to usage of
drives underlying data directories?

My second question has to do with RAID striping.  Would it be more useful
to stripe the disk with the commitlog or the disks with the data?  Of
course, with a single striped volume for data directories, it would be more
difficult to add capacity to the node later, as I've suggested above.

Casey

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