Dell EMC Solutions Enabler 9.2 SRDF Family CLI User Guide

Unplanned workload switch to synchronous target site: Cascaded SRDF/Star

About this task

In cascaded mode, data at the synchronous target site is always more current than the data at asynchronous target site.

NOTE:

You cannot retain the data at the asynchronous target site if you move the workload to the synchronous target site.

In the following image, loss of the workload site (NewYork) has resulted in a system state of NewJersey:Pathfail:

1. The first step varies depending on the state of the asynchronous target site (London).
   • If the asynchronous target site (London) is in Disconnected or PathFail state, skip to Step 2.
   • If the asynchronous target site (London) is in Protected state, issue a disconnect command from a Star control host at the synchronous target site (NewJersey) to get the asynchronous site to the PathFail state:

     symstar -cg StarGrp disconnect -trip -site London

2. From a Star control host at the synchronous target site (NewJersey), issue the symstar cleanup command to clean up any internal metadata or cache remaining at the asynchronous site.

   To clean up the London site:

   symstar -cg StarGrp cleanup -site London

3. From a Star control host at the synchronous target site (NewJersey), issue the symstar switch command to start the workload at the specified site. The following command:
   • Specifies NewJersey as the new workload site (-site NewJersey)
   • Retains the data at the NewJersey data instead of the London data (-keep_data NewJersey):

   symstar -cg StarGrp switch -site NewJersey -keep_data NewJersey

   The following image shows the resulting SRDF/Star state:

   

4. If data is protected with BCV devices, make a TimeFinder/Clone or TimeFinder/Mirror copy.

   For details, see Step 7: (Optional) Add BCV devices to the SRDF/Star configuration.

5. After the switch, you can bring up SRDF/Star in a cascaded mode or reconfigure to come up in concurrent mode. The following examples explain the steps required for each mode:
   • Proceed to Step 6 to bring up SRDF/Star in cascaded mode (the default).
   • Skip to Step 8 to reconfigure SRDF/Star in concurrent mode.
6. From a Star control host at the new workload site (NewJersey), issue two connectconnect commands to:
   • Connect NewJersey to NewYork (synchronously)
   • Connect NewYork to London (asynchronously):

   symstar -cg StarGrp connect -site NewYork
   symstar -cg StarGrp connect -site London

   The following image shows the resulting SRDF/Star state:

   

7. From a Star control host at the new workload site (NewJersey), issue two protect commands and the enable command to:
   • Protect NewJersey to NewYork
   • Protect NewJersey to London
   • Enable SRDF/Star

   symstar -cg StarGrp protect -site NewYork
   symstar -cg StarGrp protect -site London
   symstar -cg StarGrp enable

   The following image shows the resulting SRDF/Star state:

   

8. From a Star control host at the new workload site, issue the symstar reconfigure command from the workload site to change the mode to concurrent.

   See Recover using reconfigure operations.

   To reconfigure SRDF/Star to operate in concurrent mode with:

   • The workload at NewJersey,
   • The synchronous target site at NewYork, and
   • The asynchronous target site at London:

   symstar -cg StarGrp reconfigure -site London -path NewJersey:London

   The following image shows the resulting SRDF/Star configuration:

   

9. Run the following commands from a Star control host at the new workload site (NewJersey) to:
   • Connect NewJersey to NewYork (synchronously)
   • Connect NewJersey to London (asynchronously)
   • Protect NewJersey to NewYork
   • Protect NewJersey to London
   • Enable SRDF/Star

   symstar -cg StarGrp connect -site NewYork 
   symstar -cg StarGrp connect -site London 
   symstar -cg StarGrp protect -site NewYork 
   symstar -cg StarGrp protect -site London 
   symstar -cg StarGrp enable

   The following image shows the resulting SRDF/Star configuration: