Hi all,

I want to make you aware of the Fast EC team's proposal to end support for some erasure code plugins and techniques.

We want to do this for a few reasons:

1. Continuing to support a large list of plugins and techniques requires development and test effort. We don't think this effort is valuable because

2. Telemetry data shows that most Ceph clusters that are using EC are using Jerasure reed_sol_van or ISA-L reed_sol_van, and

3. Benchmarking shows that reed_sol_van has very good performance on modern CPUs.

We are proposing that the following list of plugins and techniques should be deprecated in the Umbrella release, and support be removed in the V release:

Jerasure (reed_sol_r6_op, cauchy_orig, cauchy_good, liberation, blaum_roth, liber8tion)
SHEC
CLAY

The following list of plugins and techniques would continue to be supported in the V release:

Jerasure (reed_sol_van)
ISA-L (reed_sol_van, cauchy)
LRC (Although Fast EC doesn’t currently support LRC and we wouldn't recommend using LRC yet, we think we will be able to use it in future to improve support for erasure coded pools in stretched clusters.)

I have written a post for the ceph.io blog which contains more details and shows some of the data behind the proposal. It also talks about the pool migration feature we are planning to add in Umbrella. This can be used to migrate data from a pool to a new EC pool that uses a supported plugin/technique. You can find the blog PR here: https://github.com/ceph/ceph.io/pull/988

We are interested to hear if anyone has any objections to this plan. Please reply to this mail or leave a comment on the blog PR if you do have any objections or concerns. We plan to publish the blog post sometime mid-January.

Thanks,

Jamie Pryde

Software Engineer

IBM UK

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