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Doron
Asked: 2017-05-08 23:57:19 +0800 CST

MongoDB on EC2 - R3 vs R4

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I have a 3 nodes RS on EC2. All the nodes are running on r3.2xlarge, which has EBS Optimized turned on.

Recently, AWS released the r4 series, which is described as a better version of r3 - faster memory, better networking, lower costs. However, the r4 series doesn't have the EBS Optimized option. It does have "12 Gbps of dedicated throughput to EBS".

Is it a good idea to move the nodes to the r4 series or the EBS Optimized option is crucial (and not overcome'd by the dedicated throughput to EBS)?

amazon-ec2

1 Answers

  1. All current "4" instances including R4 are EBS optimized by default, as are the i3 (high I/O), p3 (GPU compute), and f1 (fpga).

    It would be easier if AWS used the number to indicate release year, but it's just incremented when an instance type is improved.

    A large MongoDB server could benefit from the fast SSDs and very high IOPS of the i3 instance store. An r4.2xl is $0.53c/h. The i3.xl is $0.31 and gets 2M IOPS, the i3.2xl is $0.62 and gets 4M IOPS. If you're I/O limited they could be provide significantly improved performance.

    Unlike EBS which is persistent, the instance store can be lost if the instance fails, and is lost on stop/start - but not restart. That means you have to persist it some other way. Perhaps:

    • MongoDB replica set
    • You could manually set up a read replica on a smaller instance, and some kind of system to fail over to the other instance restore the primary if it fails
    • Another i3, and either failover or application awareness of multiple instances
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