content_image/988637.jpg
Table 6-1 lists the bitmap space default configuration. 

<img src='content_image/988637.jpg'>

a. The actual amount of functionality might increase based on settings, such as grain size and strip size. RAID is subject to a 15% margin or error. 

b. Remote copy includes Metro Mirror, Global Mirror, and active-active relationships. 

c. FlashCopy includes the FlashCopy function, Global Mirror with change volumes, and active-active relationships. 

The sum of all bitmap memory allocation for all functions except FlashCopy must not exceed 552 MiB. 

## 6.1.5 Thin-provisioned volumes 

Volumes can be configured to be thin-provisioned or fully allocated. A thin-provisioned volume behaves as though application reads and writes were fully allocated. When a thin-provisioned volume is created, the user specifies two capacities: 

GLYPH<SM590000> The real physical capacity that is allocated to the volume from the storage pool 

GLYPH<SM590000> Its virtual capacity that is available to the host 

In a  fully allocated  volume, these two values are the same. 

Therefore, the real capacity determines the quantity of MDisk extents that is initially allocated to the volume. The virtual capacity  is the capacity of the volume that is reported to all other IBM Spectrum Virtualize components (for example, FlashCopy, cache, and remote copy), and to the host servers. 

The  real capacity  is used to store the user data and the metadata for the thin-provisioned volume. The real capacity can be specified as an absolute value, or as a percentage of the virtual capacity. 

