content_image/979880.jpg
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. 

## 5.5.3 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. 

Figure 5-38 shows the attributes of a volume and Volume Mirroring. 

<img src='content_image/979880.jpg'>

In Figure 5-38, XIV and IBM DS8700 illustrate that a mirrored volume can use different storage devices. 

## 5.5.4 Volume Mirroring synchronization options 

As soon as a volume is created with two copies, copies are in the out-of-sync  state. The primary volume copy (located in the first specified storage pool) is defined as in sync and the secondary volume copy as out of sync. The secondary copy is synchronized through the synchronization process. 

