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From "Durity, Sean R" <>
Subject RE: [EXTERNAL] multiple Cassandra instances per server, possible?
Date Thu, 18 Apr 2019 13:45:50 GMT
What is the data problem that you are trying to solve with Cassandra? Is it high availability?
Low latency queries? Large data volumes? High concurrent users? I would design the solution
to fit the problem(s) you are solving.

For example, if high availability is the goal, I would be very cautious about 2 nodes/machine.
If you need the full amount of the disk – you *can* have larger nodes than 1 TB. I agree
that administration tasks (like adding/removing nodes, etc.) are more painful with large nodes
– but not impossible. For large amounts of data, I like nodes that have about 2.5 – 3
TB of usable SSD disk.

It is possible that your nodes might be under-utilized, especially at first. But if the hardware
is already available, you have to use what you have.

We have done multiple nodes on single physical hardware, but they were two separate clusters
(for the same application). In that case, we had  a different install location and different
ports for one of the clusters.

Sean Durity

From: William R <>
Sent: Thursday, April 18, 2019 9:14 AM
Subject: [EXTERNAL] multiple Cassandra instances per server, possible?

Hi all,

In our small company we have 10 nodes of (2 x 3 TB HD) 6 TB each, 128 GB ram and 64 cores
and we are thinking to use them as Cassandra nodes. From what I am reading around, the community
recommends that every node should not keep more than 1 TB data so in this case I am wondering
if it is possible to install 2 instances per node using docker so each docker instance can
write to its own physical disk and utilise more efficiently the rest hardware (CPU & RAM).

I understand with this setup there is the danger of creating a single point of failure for
2 Cassandra nodes but except that do you think that is a possible setup to start with the

Except the docker solution do you recommend any other way to split the physical node to 2
instances? (VMWare? or even maybe 2 separate installations of Cassandra? )

Eventually we are aiming in a cluster consisted of 2 DCs with 10 nodes each (5 baremetal nodes
with 2 Cassandra instances)

Probably later when we will start introducing more nodes to the cluster we can decommissioning
the "double-instaned" ones and aim for a more homogeneous solution..

Thank you,



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