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Host attachment: AIXprod1 | Host attachment: AIXprod2 |
Volume group: | Volume group: |
Volume group: |
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Host att: Test |
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Host att: Prog |
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Volume group: docs |
Figure 4-10 Host attachments and volume groups
Figure 4-10 shows the relationships between host attachments and volume groups. Host AIXprod1 has two HBAs, that 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 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.
4.2.9 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 which 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.
This new virtualization concept provides for much more flexibility. Logical volumes can dynamically be created and deleted. They can be grouped logically to simplify storage management. Large LUNs and CKD volumes reduce the total number of volumes and this also contributes to a reduction of the management efforts.
Figure 4-11 on page 80 summarizes the virtualization hierarchy.
Chapter 4. Virtualization concepts | 79 |
