Chapter 7. Volumes 269
7.3.3  General pane
The General pane is shown in Figure 7-22.
Figure 7-22   Custom volume creation – General pane
This pane gives the following options:
/SM590000Format volume: Controls whether the volume is formatted before being made available; 
defaults to Enabled.
/SM590000Cache mode: Controls volume caching; defaults to Enabled. Other available options are 
Read-only and Disabled.
/SM590000OpenVMS UDID: Each OpenVMS Fibre Channel-attached volume requires a user-defined 
identifier or unit device identifier (UDID). A UDID is a nonnegative integer that is used in 
the creation of the OpenVMS device name.
7.4  HyperSwap volumes
The HyperSwap function provides highly available volumes accessible through two sites at up 
to 300 km (186.4 miles) apart. A fully independent copy of the data is maintained at each site. 
When data is written by hosts at either site, both copies are synchronously updated before the 
write operation completion is reported to the host. The HyperSwap function automatically 
optimizes itself to minimize data transmitted between sites and to minimize host read and 
write latency.
If the nodes or storage at either site go offline, the HyperSwap function automatically fails 
over access to the other copy. The HyperSwap function also automatically resynchronizes the 
two copies when possible.
The HyperSwap function is built on the foundation of two earlier technologies: Non-Disruptive 
Volume Move (NDVM) function that was introduced in IBM Spectrum Virtualize V6.4, and the 
Remote Copy features that include Metro Mirror, Global Mirror, and Global Mirror with Change 
Volumes.
Note: Consider the compression guidelines in Chapter 10, “Advanced features for storage 
efficiency” on page 403 before creating the first compressed volume copy on a system.