====== 3 Site Replication ======

FIXME **Documenation in Progress** FIXME

As of version 8.1.11 TSM/ISP still does not provide Replication to two other sites. In this abstract I'll outline how to establish a workaround.

 ===== Set-Up =====
For this workaround we assume one primary server that should replicate it's data to two other sites in parallel:

{{ :en:services:storage_services:backup:tsm:admin:workarounds:3-Site-Parallel-Replication.png | 3 site replication to 2 secondary sites in parallel (3SPR)}}

but no no chain replication (//at first glance//):

{{ :en:services:storage_services:backup:tsm:admin:workarounds:3-Site-Chain-Replication.png | 3 site chain replication (3SCR) }}
===== HowTo / Approaches =====
==== 3 Site Parallel Replication (3SPR) ====
=== basic idea ===
The idea is to break up the replication relationship to the 2nd site and redefine it, using the 3rd site. afterwards break it up again and redefinde it using the 2nd site's server defintion.
=== implementation ===
assuming one node to replicate, named ''3sitepoc''
== replication tsm0 => tsm1==
<code>
REMove    REPLNode   3sitepoc
SET       REPLSERVer tsm1
UPDate    Node       3sitepoc REPLState=ENable
REPLicate Node       3sitepoc 
</code>
== replication tsm0 => tsm2==
<code>
REMove    REPLNode   3sitepoc
SET       REPLSERVer tsm2
UPDate    Node       3sitepoc REPLState=ENable
REPLicate Node       3sitepoc
</code>
== automated Replication==
The easiest way to automate the replication to both sides is to put the commands mentions above in a script and let it run as often as needed using a administrative schedule.
Taking "tsm1" as the default failover site, the script should first replicate the data to "site 2" as it finishes with "tsm1" as set replserver:
<code>
/* first replicate to 3rd  site */
REMove    REPLNode   3sitepoc
SET       REPLSERVer tsm2
UPDate    Node       3sitepoc REPLState=ENable
REPLicate Node       3sitepoc Wait=Yes
/* second replicate to failover site */
REMove    REPLNode   3sitepoc
SET       REPLSERVer tsm1
UPDate    Node       3sitepoc REPLState=ENable
REPLicate Node       3sitepoc Wait=Yes
</code>
==== 3 Site Chain Replication (3SCR) ====