CODEWITHSUNDEEP
javacassandrajvmcloudgoogle-compute-engine
user2924127
user2924127

Reputation: 6242

Cassandra - many small or fewer bigger nodes?

I will be hosting my Cassandra database on Google cloud. Instances are priced in a linear fashion meaning 1cpu with 2gb ram is $1, 2cpu with 4gb is $2, 4cpu with 8GB is $4 and so on.

I am deciding on the size of my instances and am not sure what the standard is? I was thinking of using more fewer larger instances (8cpu, 64gb) opposed to lighter such as (2cpu, 4 gb). My thought process is with more instances each node will carry less of the overall data which would have a smaller impact if nodes fail. As well, the os of these smaller instances would have less overhead because it would accept less connections.

These are pros, but here are some cons I can think of: 1) Each instance will be less utilized 2) Cassandra + JVM overhead on so many instances can add up and be a lot of overhead. 3) I will be using local SSD opposed to persistent SSD which are much more expensive meaning each instance will need their own local SSD which raises costs.

These are some reasons I can think of, is there any other pros/cons between choosing more smaller instances vs fewer larger for a Cassandra database (maybe even nodes in general)? Are there any best practices associated to choosing Cassandra server sizes?

PS: I added the 'Java' tag because Cassandra is built using JAVA and runs on the JVM and would like to see if the JVM has any pros/cons.

Upvotes: 3

Views: 569

Answers (1)

Caleb Rackliffe
Caleb Rackliffe

Reputation: 575

I think you've hit some of the tradeoff points, but here are a few other things:

  1. As the amount of data stored on a single node increases, the cost of bootstrapping (adding new nodes) increases. For instance, you'll get reasonable bootstrapping times storing 100 GB per node, but the process will take eons with 10 TB per node.
  2. SSD usage makes this less important, but consider using separate physical disks for your commitlog and data.
  3. Configurations with fewer than 4 cores or less than 8 GB of memory are usually not recommended, but your mileage may vary.

Upvotes: 6

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