Creating extent pools for fixed block volumes using the DS CLI

Complete this task to create fixed block volume extent pools. This is the first step in configuring new fixed block storage. You can use the DS CLI commands to create extent pools for fixed block volumes.

Creating the extent pools before the arrays and ranks saves a processing step. When you create the new ranks, you can assign them to existing extent pools. Otherwise, you must modify each rank object to complete the extent pool ID assignment after the extent pools have been defined.

Each extent pool is defined with the rank group of 0 or 1 and a storage type of fb. You must define one extent pool for each rank group and storage type combination. This means that you must make a minimum of two extent pools for a storage unit that contains fixed block storage: one fixed block extent pool per rank group.

Extent pools that are defined for rank group 0 or 1 are assigned an even- or odd-numbered extent pool ID, respectively. Even-numbered extent pools are managed by storage server ID 0. Odd-numbered extent pools are managed by storage server ID 1. Each rank is assigned to one extent pool; therefore, storage server workload is affected by the rank assignments to even- and odd-numbered extent pool IDs. It is better to evenly distribute rank and extent pool allocations in order to keep the storage server workloads balanced.

You can create more than the minimum number of extent pools. For example, you can define unique extent pools for each RAID type (5 or 10) that is configured in a storage image. Or, you can define and name extent pools according to the host system attachments that access the volumes that are created from extent pool extents. You can have the same number of extent pools as ranks.

i5/OS considerations

i5/OS supports only specific volume sizes and these might not be an exact number of extents. i5/OS volumes are defined in decimal gigabytes (10^9 bytes). You can use the following table when you are creating the logical volumes for use with i5/OS. You will notice that in almost every case, the i5/OS device size does not match a whole number of extents, so some space can be wasted for you specific configuration.

Pro- tected Model Type	Unpro- tected Model Type	i5/OS Device size (dec- imal giga- bytes)	Number of LBAs	Extents	Unus- able space (binary giga- bytes)	Usable space%
xxxx-A01	xxxx-A81	8.5	16 777 216	8	0.00	100.00
xxxx-A02	xxxx-A82	17.5	34 275 328	17	0.66	96.14
xxxx-A05	xxxx-A85	35.1	68 681 728	33	0.25	99.24
xxxx-A04	xxxx-A84	70.5	137 822 208	66	0.28	99.57
xxxx-A06	xxxx-A86	141.1	275 644 416	132	0.56	99.57
xxxx-A07	xxxx-A87	282.2	551 288 832	263	0.13	99.95

Note: Only Ax2, Ax4 and Ax5 models are supported as external LSU LUNs.

Use the lsextpool and mkextpool commands to create the fixed block extent pools. You must be logged into the DS CLI application and connected to the storage unit that will be used for open systems host system storage.

Perform the following steps to create the fixed block extent pools. The example commands displayed in this task are shown in two formats. The first format shows the type of information the command requires. The second format provides the command with declared values for the variables

Issue the mkextpool command to create the fixed block extent pool for rank group 0. Enter the mkextpool command at the dscli command prompt with the following parameters and variables:
```
dscli>mkextpool -dev storage_image_ID -rankgroup [0 | 1] 
-stgtype fb extent_pool_name
```
Example
```
dscli>mkextpool -dev IBM.1750-68FA120 -rankgrp 0 -stgtype fb P0
```
where P0 represents the extent pool name that you assign. This name can be 16 double-byte characters.
Press Enter. A successful process displays the following message:
```
Sun Aug 11 02:23:49 PST 2004 IBM DS CLI Version: 5.0.0.0 DS: IBM.1750-68FA120

Extent pool P0 successfully created.
```
Note: The unique name that you assigned to the extent pool does not display in the process message. However, when you issue the lsextpool command, the extent pool name is displayed.
Repeat Step 1 for each extent pool that you want to create. Try to evenly distribute rank and extent pool allocations in order to keep the storage server workloads balanced.
Verify the extent pool assignments by issuing the lsextpool command when you are done creating the extent pools. Use the -l parameter to display a full report for the extent pools that are assigned to the storage unit. Enter the lsextpool command at the dscli command prompt with the following parameters and variables:
```
dscli>lsextpool -dev storage_image_ID -l
```
Example
```
dscli>lsextpool –dev IBM.1750-68FA120 -l
```