Disk initialization performance on POWER systems

Answer

Environment:
- POWER7 (and later) system(s)
- V7000
- IBM i client partition(s) at 7.1 and later
- 2145 type disk units on IBM i partition(s)

In environments utilizing V7000 storage attached to an IBM i partition, the IBM i drive initialization times may take longer than in the past. The IBM i disk initialization buffer size is defaulted in this environment to 32K, so as to reduce the impact to other workloads running on the V7000. If there are no other workloads or other workloads with performance considerations, disk initialization time may be decreased by increasing the buffer size.

To change the buffer size, use the following System Service Tools Advanced Analysis macro:

To change the buffer size, use the following System Service Tools Advanced Analysis macro:
Note: This Advanced Analysis macro is not available on a D-mode IPL.

Caution: Changing this value may cause severe performance impacts to other workloads on the V7000.

Steps to increase the value:
1. STRSST and sign in
2. Option 1. Start a service tool <enter>
3. Option 4. Display/Alter/Dump <enter>
4. Option 1. Display/Alter storage <enter>
5. Option 2. Licensed Internal Code (LIC) data <enter>
6. Option 14. Advanced analysis <enter>
7. 1 to select iodd <enter>
8. For the options to increase the value to 2M, specify: svcformatiosize 2M <enter>


Steps to decrease the value:
1. STRSST and sign in
2. Option 1. Start a service tool <enter>
3. Option 4. Display/Alter/Dump <enter>
4. Option 1. Display/Alter storage <enter>
5. Option 2. Licensed Internal Code (LIC) data <enter>
6. Option 14. Advanced analysis <enter>
7. 1 to select iodd <enter>
8. For the options to decrease the value to 32K, specify: svcformatiosize 32K <enter>

Contact your software service provider with any questions.