Transition tiers can be added to MinIO using `mc admin tier add` command to associate a `gcs`, `s3` or `azure` bucket or prefix path on a bucket to the tier name.

`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

`xl.meta` carries first 8 bytes an XL header which describes the current format and the format version,

replication, i.e. when remote target is configured with --sync mode in `mc admin bucket remote add` does not apply to `DELETE` operations. The version being deleted on the source cluster needs to maintain state and ensure that the operation is mirrored to the target cluster prior to completing on the source object version. Since this needs to account for the target cluster availability and the need to serialize concurrent DELETE operations on different versions of the same object during multi DELETE operations,...

number then GCD algorithm provides affinity towards odd number erasure sets to provide for uniform distribution across nodes*. This is to ensure that same number of drives are pariticipating in any erasure set. For example if you have 2 nodes with 180 drives then GCD is 15 but this would lead to uneven distribution, one of the nodes would participate more drives. To avoid this the affinity is given towards nodes which leads to next best GCD factor of 12 which provides uniform distribution.

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