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98 DS8000 Series: Concepts and Architecture
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.
Figure 5-11 Host attachments and volume groups
Figure 5-11 shows 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.
WWPN-1 WWPN-2
Host attachment: AIXprod1
Volume group: DB2-1
WWPN-3 WWPN-4
Host attachment: AIXprod2
Volume group: docs
WWPN-5 WWPN-6
WWPN-7
WWPN-8
Host att: Test
Host att: Prog
Volume group: DB2-2
Volume group: DB2-test