Chapter 2. Introduction to IBM Flex System V7000 Storage Node 65
MDisks can be added to a storage pool at any time to increase the capacity of the storage
pool. MDisks can belong in only one storage pool and only MDisks in unmanaged mode can
be added to the storage pool. When an MDisk is added to the storage pool, the mode
changes from unmanaged to managed and vice versa when you remove it.
Each MDisk in the storage pool is divided into a number of extents. The size of the extent is
selected by the administrator at creation time of the storage pool and cannot be changed
later. The size of the extent ranges from 16 MB up to 8 GB.
The extent size has a direct impact on the maximum volume size and storage capacity of the
clustered system. A system can manage 4 million (4 x 1024 x 1024) extents. For example, a
system with a 16 MB extent size can manage up to 16 MB x 4 MB = 64 TB of storage.
The effect of extent size on the maximum volume size is shown inTable 2-7, and lists the
extent size and the corresponding maximum clustered system size.
Table 2-7 Maximum volume capacity by extent size
The effect of extent size on the maximum clustered system capacity is shown inTable 2-8.
Table 2-8 Extent size and effect on clustered system capacity
Extent size Maximum volume capacity for normal
volumes (GB)
16 MB 2048 (2 TB)
32 MB 4096 (4 TB)
64 MB 8192 (8 TB)
128 MB 16384 (16 TB)
256 MB 32768 (32 TB)
512 MB 65536 (64 TB)
1024 MB 131072 (128 TB)
2048 MB 262144 (256 TB)
4096 MB 528288 (512 TB)
8192 MB 1056576 (1,024 TB)
Extent size Maximum storage capacity of cluster
16 MB 64 TB
32 MB 128 TB
64 MB 256 TB
128 MB 512 TB
256 MB 1 PB
512 MB 2 PB
1024 MB 4 PB
2048 MB 8 PB
4096 MB 16 PB
8192 MB 32 PB
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