IBM DS8000 manual Extent Pool

Figure 10-5shows an example of the relationship between LSSs, extent pools, and volume groups: Extent pool 4, consisting of two LUNs, LUN 2210 and LUN 7401; and extent pool 5, consisting of three LUNs, LUN 2313, 7512, and 7515.

Here are some considerations regarding the relationship between LSS, extent pools, and volume groups:

￿Volumes from different LSSs and different extent pools can be in one volume group as shown in Figure 10-5.Volume group 1 consists of extent pool 4, LUN 2210, and extent pool 5, LUN 7512.

￿Volumes from the same LSS or the same extent pool, or both, can be in different volume groups. For example in Figure 10-5,LUN 7512 in extent pool 5 and LUN 7515 in extent pool 5, both of which reside in LSS75, also reside in different volume groups.

Extent Pool 4 Extent Pool 5

2

2

1

0

7

4

0

1

	2	7
	3	5
	Volume Group 2
	1	1
Volume Group 1	3	5
	7
	5
	1
	2

Figure 10-5 Example of relationship between LSSs, extent pools, and volume group

The LSS and LCU provide the logical grouping of volumes/LUNs for Copy Services and various other purposes. Some of these purposes are explained along with general considerations about LSSs in the DS8000, as follows:

￿The LSS or LCU determines the addressing, address groups, and PAVs.

–Each logical volume has a 4 digit Hexadecimal xyzz identification number built using the following rules: x = the address group, xy = LSS number itself, and zz = the volume id (volid). For example, LUN 2310 has an address group number of 2, is located in LSS 23, and has a volid of 10.

–There are up to 16 LSSs in an address group. For example, 00 to 0F for address group 0, 10-1F for address group 1, 20-2F for address group 2, and so forth.

–Any given PAV can only be used within one LCU.

￿LSSs are used for Copy Services, PPRC paths, and consistency group properties or time-outs.

￿There are a maximum number of LSSs. For the DS8000 there are a maximum of 255 LSSs. When speaking of ESCON, the maximum is 16 ESCON CKD LSSs.

￿The LSSs have a pre-determined association with Server0 or Server1.

–The even LSSs are associated with Server0.

–The odd LSSs are associated with Server1.

￿The LSSs are configured to be either CKD or FB.

–CKD LSSs’ definitions are configured during the LCU creation.

Chapter 10. The DS Storage Manager - logical configuration 197