You are viewing an old version of this page. View the current version.

Compare with Current View Page History

« Previous Version 5 Next »

Distributed systems basic expectation is to provide the data durability.
To provide the higher data durability, many popular storage systems use replication
approach which is expensive. The Apache Ozone supports `RATIS/THREE` replication scheme.
The Ozone default replication scheme `RATIS/THREE` has 200% overhead in storage
space and other resources (e.g., network bandwidth).
However, for warm and cold datasets with relatively low I/O activities, additional
block replicas rarely accessed during normal operations, but still consume the same
amount of resources as the first replica.

Therefore, a natural improvement is to use Erasure Coding (EC) in place of replication,
which provides the same level of fault-tolerance with much less storage space.
In typical EC setups, the storage overhead is no more than 50%. The replication factor of an EC file is meaningless.
Instead of replication factor, we introduced ReplicationConfig interface to specify the required type of replication,
either `RATIS/THREE` or `EC`.

Integrating EC with Ozone can improve storage efficiency while still providing similar
data durability as traditional replication-based Ozone deployments.
As an example, a 3x replicated file with 6 blocks will consume 6*3 = `18` blocks of disk space.
But with EC (6 data, 3 parity) deployment, it will only consume `9` blocks of disk space.

Git Branch: https://github.com/apache/ozone/tree/HDDS-3816-ec

Branch merge checklist

1. builds/intermittent test failures

There are no intermittent failures specific to the HDDS-3861-ec branch as of now. During the development , it was ensured

all the CI checks are clean prior to every commit merge .The plan is to run repeated CI checks on the merge commit to master.

2. documentation

Described feature in Apache ozone page via HDDS-5067.

3. design, attached the docs

Following design docs are linked from the documentation present in HDDS-2939 jira

4. s3 compatibility

EC feature does not beak any existing S3 compatibility.

5. docker-compose / acceptance tests

Acceptance tests added here

6. support of containers / Kubernetes:

NA. Deployment model for OzoneManager remains as earlier.

7. coverage/code quality:

Sonar master branch
Sonar HDDS-3816-ec branch.

The branch has better coverage than master (68% vs 72%)

8. build time

There is no significant difference between local build time.

Recent master build


Recent HDDS-3816-ec branch build


9. possible incompatible changes/used feature flag: 

For using this feature, users create bucket with EC replication config, so that the keys created in that bucket will be written in EC mode.

10. third party dependencies/licence changes:

No new dependencies are added.

11. performance

There should not be any performance impact for Non-EC flows. For EC files there is basic benchmark performed here.
 

12. security considerations

Everything works as earlier and there is no security implications because of the feature.





  • No labels