– It is not possible to recombine the two volumes after they have been split. 

– Adding and splitting in one workflow enables migrations that are not currently allowed. 

– The split volume copy can be used as a means for creating a point-in-time copy (clone). 

GLYPH<SM590000> Repair/validate in three ways. This compares volume copies and performs these functions: 

– Reports the first difference found. It can it erate by starting at a specific LBA by using the -startlba parameter. 

– Creates virtual medium errors where there are differences. 

– Corrects the differences that are found (reads from primary copy and writes to secondary copy). 

GLYPH<SM590000> View to list volumes affected by a back-end disk subsystem being offline: 

– Assumes that a standard use is for mirror between disk subsystems. 

– Verifies that mirrored volumes remain accessible if a disk system is being shut down. 

– Reports an error in case a quorum disk is on the back-end disk subsystem. 

GLYPH<SM590000> Expand or shrink a volume: 

– This function works on both of the volume copies at once. 

– All volume copies always have the same size. 

– All copies must be synchronized before expanding or shrinking them. 

DRP limitation:  Data Reduction Pools do not support thin/compressed volumes shrinking. 

GLYPH<SM590000> Delete a volume. When a volume gets deleted, all copies get deleted. 

GLYPH<SM590000> Migration commands apply to a specific volume copy. 

GLYPH<SM590000> Out-of-sync bitmaps share the bitmap space with FlashCopy and Metro Mirror/Global Mirror. Creating, expanding, and changing I/O groups might fail if there is insufficient memory. 

## 6.5.3 Mirrored volume components 

GLYPH<SM590000> GUI views contain volume copy identifiers. 

Note the following points regarding mirrored volume components: 

GLYPH<SM590000> A mirrored volume is always composed of two copies (copy 0 and copy1). 

GLYPH<SM590000> A volume that is not mirrored consists of a single copy (which for reference might be copy 0 or copy 1). 

A mirrored volume looks the same to upper-layer clients as a non-mirrored volume. That is, upper layers within the cluster software, such as FlashCopy and Metro Mirror/Global Mirror, and storage clients, do not know whether a volume is mirrored. They all continue to handle the volume as they did before without being aware of whether the volume is mirrored. 

