IBM DS8000 manual Summary of the virtualization hierarchy, Host attachments and volume groups

FB logical volumes may be defined in one or more volume groups. This allows a LUN to be shared by host HBAs configured to different volume groups. An FB logical volume is automatically removed from all volume groups when it is deleted.

The maximum number of volume groups is 8320 for the DS8000.

WWPN-1 WWPN-2	WWPN-3 WWPN-4
Host attachment: AIXprod1	Host attachment: AIXprod2
Volume group: DB2-1	Volume group: DB2-2
Volume group: DB2-test
Host att: Test
WWPN-5 WWPN-6
WWPN-7
Host att: Prog
WWPN-8	Volume group: docs

Figure 5-11 Host attachments and volume groups

Figure 5-11shows the relationships between host attachments and volume groups. Host AIXprod1 has two HBAs, which are grouped together in one host attachment, and both are granted access to volume group DB2®-1. Most of the volumes in volume group DB2-1 are also in volume group DB2-2, accessed by server AIXprod2. In our example, there is, however, one volume in each group that is not shared. The server in the lower left part has four HBAs and they are divided into two distinct host attachments. One can access some volumes shared with AIXprod1 and AIXprod2. The other HBAs have access to a volume group called “docs.”

5.3.8 Summary of the virtualization hierarchy

Going through the virtualization hierarchy, we started with just a bunch of disks that were grouped in array sites. An array site was transformed into an array, eventually with spare disks. The array was further transformed into a rank with extents formatted for FB or CKD data. Next, the extents were added to an extent pool that determined which storage server would serve the ranks and aggregated the extents of all ranks in the extent pool for subsequent allocation to one or more logical volumes.

Next we created logical volumes within the extent pools, assigning them a logical volume number that determined which logical subsystem they would be associated with and which server would manage them. Then the LUNs could be assigned to one or more volume groups. Finally the host HBAs were configured into a host attachment that is associated with a given volume group.

98DS8000 Series: Concepts and Architecture