8. Disconnect and remove the old volumes on the host from the old IBM FlashSystem 9100 cluster. 

9. Unmap the old volumes from the old IBM FlashSystem 9100 cluster to the host. 

This approach uses the server’s computing resources (CPU, memory, and I/O) to replicate the data. It can be done online if properly planned. Before you begin, make sure it has enough spare resources. 

The biggest benefit to using either approach is that they easily accommodate (if necessary) the replacement of your SAN switches or your back-end storage controllers. You can upgrade the capacity of your back-end storage controllers or replace them entirely, as you can replace your SAN switches with bigger or faster ones. However, you do need to have spare resources, such as floor space, power, cables, and storage capacity, available during the migration. 

## 9.6.4 Splitting an IBM FlashSystem 9100 cluster 

Splitting an IBM FlashSystem 9100 cluster might become a necessity if you have one or more of the following requirements: 

GLYPH<SM590000> To grow the environment beyond the maximum number of I/O groups that a clustered system can support. 

GLYPH<SM590000> To grow the environment beyond the maximum number of attachable subsystem storage controllers. 

GLYPH<SM590000> To grow the environment beyond any other maximum system limit. 

GLYPH<SM590000> To achieve new levels of data redundancy and availability. 

By splitting the clustered system, you no longer have one IBM FlashSystem 9100 system that handles all I/O operations, hosts, and subsystem storage attachments. The goal is to create a second IBM FlashSystem 9100 system so that you can equally distribute the workload over the two systems. 

After safely removing enclosures from the existing cluster and creating a second IBM FlashSystem 9100 system, choose from the following approaches to balance the two systems: 

GLYPH<SM590000> Attach new storage subsystems and hosts to the new system, and start putting only new workload on the new system. 

GLYPH<SM590000> Migrate the workload onto the new system by using the approach described in 9.6.3, “Moving to a new IBM FlashSystem 9100 cluster” on page 347. 

## 9.7 Adding expansion enclosures 

If you plan well, you can buy an IBM FlashSystem 9100 product with enough internal storage to run your business for some time. But as time passes and your environment grows, you will need to add more storage to your system. 

Depending on the IBM FlashSystem 9100 product and the code level that you have installed, you can add different numbers of expansion enclosures to your system. Because all IBM FlashSystem 9100 systems were designed to make managing and maintaining them as simple as possible, adding an expansion enclosure is an easy task. 

