code: func (schemas Schemas) MaxChunkSpan() uint32 {
  	max := uint32(0)
  	for _, s := range schemas.raw {
  		for _, r := range s.Retentions {
  			max = util.Max(max, r.ChunkSpan)
  		}
  	}
  	for _, r := range schemas.DefaultSchema.Retentions {
  		max = util.Max(max, r.ChunkSpan)
  	}
  	return max
  }
docs: // MaxChunkSpan returns the largest chunkspan seen amongst all archives of all schemas