Parallel Sysplex InfiniBand (PSIFB) links are the latest Coupling Facility links. They were announced in February 26, 2008 in US Hardware Announcement 108-154, “IBM System z10 Enterprise Class – The forward-thinking mainframe for the twenty-first century” as well as in the May 6, 2008 US Hardware Announcement 108-269, “IBM System z10 Enterprise Class: Helping to meet global 24x7 demands for information services with improvements for Internet access and coupling,”
There are several ways of classifying IFB links. It can be Double Data Rate (DDR) or Single Data Rate (SDR). The IFB links can also be characterized by the amount of lanes of communication within each physical link. For example, 12x links provide 12 lanes of communication within each physical link. 1x links provide a single lane of communication within each physical link.
There are many reasons for migrating to PSIFB links.
- The 12x links are supported up to 150 meters. This extends high speed coupling beyond the 10 meters supported by ICB-4 links.
- The 1x links are supported up to 10 kilometers (km) unrepeated. Further distances are supported with qualified DWDM vendors. The list of qualified venders can be found on ResourceLink (PDF, XX KB)
Like other coupling links, external InfiniBand coupling links support time synchronization signals for Server Time Protocol (STP).
The support plans for the System z servers are:
| System z9 |
System z10 |
Comments |
| 12x SDR |
12x DDR |
Supports distance of up to 150 m
Auto-negotiates down to SDR if connecting a System z10 to a System z9 |
| |
1x DDR
1x DDR |
Designed to complement and/or replace ISC-3 links. Supports unrepeated distance of up to 10 km
Depending on the capability of the attached DWDM, the link data rate will automatically be set to either SDR or DDR. |
The supported configurations for 12X PSIFB links can be seen in this matrix.
| |
z/OS |
z890
z990 |
System z9 |
System z10 |
| CF |
|
|
|
|
| z890 / z990 |
|
n/a |
n/a |
n/a |
| System z9 |
|
n/a |
No |
Yes¹ |
| System z10 |
|
n/a |
SOD² |
Yes |
1. IBM currently supports System z10 connectivity to a System z9 with a stand-alone CF.
2. IBM currently intends to support z/OS on a System z9 to connect to a CF on a System z10.
Note the SOD in IBM US Hardware Announcement 108-154 dated February 26, 2008, that IBM intends to make available 12x IB links on general purpose System z9 servers. System z10 connectivity to general purpose System z9 servers.
1x PSIFB links are not supported on System z9 servers and can only be used to connect System z10 to other System z10 servers.
Specifically, a comparison of the effect of the links relative performance can be seen in the table below.
This table assumes:
- The CF activity rate to the coupling facility is 9 operations per million instructions, or 9 operations/second per MIPS of the server. This is typical for a high end data sharing environment. If the activity rate is less, then the values shown in the table should be proportionally less.
- Heuristic Synchronous to Asynchronous conversion is not taken into account. This would limit the coupling overhead to about 18%.
- Shown is data for a non-System-Managed duplexing environment.
| Host CF |
z890 |
z990 |
z9 BC |
z9 EC |
z10 EC |
| z890 ISC |
13% |
15% |
16% |
17% |
21% |
| z890 ICB/IC |
9% |
10% |
10% |
11% |
13% |
| z990 ISC |
13% |
14% |
14% |
15% |
19% |
| z990 ICB/IC |
9% |
9% |
9% |
10% |
13% |
| z9 BC ISC |
12% |
13% |
14% |
15% |
19% |
| z9 BC CIB |
NA |
NA |
NA |
NA |
14% |
| z9 BC ICB/IC |
8% |
9% |
9% |
10% |
12% |
| z9 EC ISC |
12% |
13% |
13% |
14% |
18% |
| z9 EC CIB |
NA |
NA |
NA |
NA |
14% |
| z9 EC ICB/IC |
8% |
8% |
8% |
9% |
11% |
| z10 EC ISC |
11% |
12% |
12% |
13% |
17% |
| z10 EC CIB |
NA |
NA |
NA |
NA |
13% |
| z10 EC ICB/IC |
7% |
7% |
7% |
8% |
10% |
The performance “CIB” links, or “Coupling over InfiniBand” as PSIFB is known to the IOCDS and to RMF reports, come in about half way between ISC-3 and ICB-4 links.
More information can be obtained from:
Redbook
White Paper
| 
