Chapter 6. Volume configuration 295
Table 6-1 shows you the bitmap space default configuration.
Table 6-1 Bitmap space default configuration
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:
The real physical capacity that is allocated to the volume from the storage pool
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.
Copy service Minimum
allocated
bitmap
space
Default
allocated
bitmap
space
Maximum
allocated
bitmap
space
Minimum
a
functionality
when using the default
values
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.
Remote copy
b
b. Remote copy includes Metro Mirror, Global Mirror, and active-active relationships.
0 20 MiB 512 MiB 40 TiB of remote mirroring
volume capacity
FlashCopy
c
c. FlashCopy includes the FlashCopy function, Global Mirror with change volumes, and
active-active relationships.
0 20 MiB 2 GiB 10 TiB of FlashCopy
source volume capacity
5 TiB of incremental
FlashCopy source volume
capacity
Volume
mirroring
0 20 MiB 512 MiB 40 TiB of mirrored volumes
RAID 0 40 MiB 512 MiB 80 TiB array capacity
using RAID 0, 1, or 10
80 TiB array capacity in
three-disk RAID 5 array
Slightly less than 120 TiB
array capacity in five-disk
RAID 6 array
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