These channels are maintained and updated as nodes and links appear and disappear from  the fabric, and are repaired to maintain operation where possible. If communication between  the systems is interrupted or lost, an event is logged (and the MM/GM relationships stop). Alerts:  You can configure the system to raise Simple Network Management Protocol  (SNMP) traps to the enterprise monitoring system to alert on events that indicate an  interruption in internode communication occurred.  All IBM SAN Volume Controller nodes maintain a database of other devices that are visible on  the fabric. This database is updated as devices appear and disappear. Devices that advertise themselves as IBM SAN Volume Controller or Storwize V7000 nodes  are categorized according to the system to which they belong. Nodes that belong to the same  system establish communication channels between themselves and exchange messages to  implement clustering and the functional protocols of IBM Spectrum Virtualize. Nodes that are in separate systems do not exchange messages after initial discovery is  complete, unless they are configured together to perform a remote copy relationship. The intercluster link carries control traffic to coordinate activity between two systems. The link  is formed between one node in each system. The traffic between the designated nodes is  distributed among logins that exist between those nodes. If the designated node fails (or all of its logins to the remote system fail), a new node is  chosen to carry control traffic. This node change causes the I/O to pause, but it does not put  the relationships in a  ConsistentStopped  state. Note:  Use the  chsystem  command with  -partnerfcportmask  to dedicate several FC ports  only to system-to-system traffic to ensure that remote copy is not affected by other traffic,  such as host-to-node traffic or node-to-node traffic within the same system. Metro Mirror establishes a synchronous relationship between two volumes of equal size. The  volumes in a Metro Mirror relationship are referred to as the  master  (primary) volume and the  auxiliary  (secondary) volume. Traditional FC Metro Mirror is primarily used in a metropolitan  area or geographical area, up to a maximum distance of 300 km (186.4 miles) to provide  synchronous replication of data.  With synchronous copies, host applications write to the master volume, but they do not  receive confirmation that the write operation completed until the data is written to the auxiliary  volume. This action ensures that both the volumes have identical data when the copy  completes. After the initial copy completes, the Metro Mirror function always maintains a fully  synchronized copy of the source data at the target site. Metro Mirror has the following characteristics: Increased distance directly affects host I/O performance because the writes are synchronous.  Use the requirements for application performance when you are selecting your Metro Mirror  auxiliary location. Chapter 11. Advanced Copy Services  547 GLYPH<SM590000> Zero recovery point objective (RPO) GLYPH<SM590000> Synchronous GLYPH<SM590000> Production application performance that is affected by round-trip latency 11.6.5 Metro Mirror overview Intercluster links