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198 DS8000 Series: Concepts and Architecture
– FB LSSs’ definitions are configured during the volume creation.
LSSs have no predetermined relation to physical ranks or extent pools other than their
server affinity to either Server0 or Server1.
– One LSS can contain volumes/LUNs from different extent pools.
– One extent pool can contain volumes/LUNs that are in different LSSs, as shown in
Figure 10-6.
– One LCU can contain CKD volumes/LUNs of different types, for example, type 3390
Model 3 and Model 9.
– LSSs can have a many-to-many Copy Services relationship as shown by the arrows in
Figure 10-6.
Figure 10-6 Example of Copy Services relationship between LSSs in the same storage image
An entire address group will be either FB or CKD; for example, all 16 LSSs in that group
would be either FB or CKD type LSSs.
Initially there will only be 8 address groups for the DS8000 at GA, however more will be
available at a later time.
One address group has 4096 addresses (16 LSS x 256 logical volume = 4096 logical
volumes or addresses). This means that if you had eight address groups, you would have
32768 (8 X 4096 = 32768) addresses, which translates to 32768 logical volumes or
addresses.
As an example: When creating a logical volume from an extent pool built with FB ranks, the
GUI will prompt for which LSS this FB volume will be placed in, and will propose a list of
LSSs. If the user chooses LSS 14 and if it is the first LUN to be placed in this LSS, then the
attributes of address group 1 will be Fixed Block, reserving LSS 10 to 1F for Fixed Block
volumes. The user will not be able to create any LCU using address group 1.
Attention: The address groups and LSSs are predefined in the DS8000. Initially, they do
not have any data format attributes (FB or CKD). Their data format attributes are set when
the first LUN is added to one LSS in an unused address group or when you create an LCU
using an unused address group.
When creating a logical volume, the user is prompted to add the volume to an LSS. Adding
the volume to an unused LSS will set its data format characteristics (FB or CKD) and also
will set the address group data format characteristics. It also sets the data format of the
remaining 15 LSSs in that address group.
2
3
1
0
7
5
0
1
Extent Pool 3
Rank1
2
3
1
3
7
5
1
2
Extent Pool 5
Rank3
5
1
1
1
7
5
0
2
Copy services Relationships