IBM DS8000 manual Extent Pool

–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.

Extent Pool 5	Extent Pool 3
Rank3		Rank1
2	2	5
3	3	1
1	1	1
3	0	1
7	7	7
5	5	5
1	0	0
2	1	2
Copy services Relationships

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.

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.

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.

198DS8000 Series: Concepts and Architecture