Alexis,

Thanks! We joined the Storage WG and will work with Ben on CSI and future
projects.

The use case was running Rook Block storage on-top of ephemeral/instance
storage on EC2 instances vs. using EBS storage. Rook would handle the
replication of data across instances and stripe across them for performance.
Pods in the cluster would see this like any other volume.

For Pod failover, the detach / detach cycle is much faster than EBS. One of
our users compared EBS to Rook [1] and showed that Rook volume failover
happened in less than minutes vs. up to an hour with EBS.

Also EBS volumes only support a single writer (ReadWriteOnce in K8S) which
makes them a poor candidate for hot failover scenarios underneath, say,
Postgres or MySql. With the work we’re doing on the Rook Volume Plugin [2]
we plan to support ReadWriteMany to support a hotter failover where the
app/service ontop can handle the fencing.

Finally, there are cost and performance tradeoffs for running on-top of
ephemeral/instance storage vs. EBS. For example, a lot of the instance
storage is unused in most deployments and has a high performance.

Happy to discuss in more detail.

Thanks!
Bassam

[1] https://gitter.im/rook/rook?at=58baff6f872fc8ce62b6ee26
[2] https://github.com/kubernetes/kubernetes/pull/46843


On Jun 6, 2017, at 9:03 AM, Alexis Richardson <alexis@...> wrote:

Bassam

It would be good for Rook team to join Storage WG, if you haven't done so
yet.

QQ: you said that k8s use cases that run on EBS have high failover
times & that you can improve this. I missed the details of that. Can
you say more please?

alexis