## Description of `xl.meta`

`xl.meta` is a new self describing backend format used by MinIO to support AWS S3 compatible versioning.
This file is the source of truth for each `version` at rest. `xl.meta` is a msgpack file serialized from a
well defined data structure. To understand `xl.meta` here are the few things to start with

default sync metadata changes on a object version marked `REPLICA` back to source. This requires a setting in the replication configuration called [replica modification sync](https://aws.amazon.com/about-aws/whats-new/2020/12/amazon-s3-replication-adds-support-two-way-replication/).

For active-active replication, automatic failover occurs on `GET/HEAD` operations if object or object version requested qualifies for replication and is missing on one site, but present on the other. This allows the...

custom name derived from a randomly generated uuid - e.g. `0b/c4/0bc4fab7-2daf-4d2f-8e39-5c6c6fb7e2d3`. The first two prefixes are characters 1-2,3-4 from the uuid. This format allows tiering to any cloud irrespective of whether the cloud in question supports versioning. The reference to the transitioned object name and transitioned tier is stored as part of the internal metadata for the object (or its version) on MinIO.

Extra metadata maintained internally in `xl.meta` for a transitioned object...

- Erasure set is a single erasure coding unit within a MinIO deployment. An object is sharded within an erasure set. Erasure set size is automatically calculated based on the number of drives. MinIO supports unlimited number of drives but each erasure set can be upto 16 drives and a minimum of 2 drives.