IBM DS8000 manual Extent Pool

Extent Pool

2

3

1

0

7

5

0

1

1GB Extents

Ranks formated for FB data

Figure 10-2 An extent pool containing 2 volumes

Figure 10-2is an example of one extent pool composed of ranks formatted for FB data. Two logical volumes are defined (volumes 2310 and 7501). Each volume is made up of 6 extents at 1 GB each. This makes each volume 6 GBs. The numbering sequence of LUN id 2310, shown in the diagram as the top volume, translates into an address. The volume identification number is built using the following rules: xyzz, x = the LSS 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.

Different volumes on a single extent pool can be assigned to the same or different LSSs.

Extent pools are assigned to server 0 and server 1 during configuration and receive their server affinity at this time. If you are using the custom configuration, we recommend, for user manageability reasons, that you associate the rank even numbers to server 0 and the rank odd numbers to server 1 when defining the extent pools during the configuration process.

The following rules apply when creating extent pools:

￿You must configure a minimum of two extent pools to utilize server 0 and server 1.

￿More than one rank can reside in an extent pool, but you cannot make two extent pools out of only one rank. We recommend that you create one extent pool out of one rank, unless the LUN capacity is greater than the capacity of one rank in the extent pool.

Some general considerations are:

￿One rank per pool will not constrain addresses.

￿Ranks can be added to an extent pool at any time.

￿The logical volumes defined in one extent pool can be in different LSSs.

￿The logical volumes in different extent pools can be in the same LSS; they are limited only by the odd and even server affinity.

￿Ranks can be removed from an extent pool if no extents on the rank are currently assigned to the logical volumes.

￿Any extent can be used to make a logical volume.

Chapter 10. The DS Storage Manager - logical configuration 193