text: Figure 3-11 Correct volume relationship 
  
  The back-end storage systems at the replication target site must be capable to handle the 
  peak application workload to the replicated volumes, plus the client-defined level of 
  background copy, plus any other I/O being performed at the remote site. The performance of 
  applications at the local clustered system can be limited by the performance of the back-end 
  storage controllers at the remote site. This consideration is especially important for Metro 
  Mirror replication. 
  
  A complete review must be performed before Serial Advanced Technology Attachment 
  (SATA) drives are used for any Metro Mirror or Global Mirror replica volumes. If a slower disk 
  subsystem is used as target for the remote volume replicas of high-performance primary 
  volumes, the Storwize V7000 cache might not be able to buffer all the writes. The speed of 
  writes to SATA drives at the remote site might limit the I/O rate at the local site. 
  
  To ensure that the back-end storage can support the data replication workload, you can 
  dedicate back-end storage systems to only Global Mirror volumes. You can also configure the 
  back-end storage to ensure sufficient quality of service (QoS) for the disks that are used by 
  Global Mirror. Alternatively, you can ensure that physical disks are not shared between data 
  replication volumes and other I/O. 