HiperSockets

Mainframe HiperSockets is a technology that provides high-speed TCP/IP connectivity within a central processor complex. It eliminates the need for any physical cabling or external networking connection between servers running in different LPARs.

The communication is through the system memory of the processor, so servers are connected to form a "internal LAN."

The HiperSockets implementation is based on the OSA-Express Queued Direct I/O (QDIO) protocol, hence HiperSockets is also called internal QDIO, or IQDIO. The microcode emulates the link control layer of an OSA-Express QDIO interface.

Figure 1 shows how to use HiperSockets; of particular note is that z/OS is not the only operating system running on a mainframe host that can take advantage of HiperSockets. Other operating systems include z/VM and Linux.

Note: z/VM is capable of functioning very similar to an LPAR. Instead of doing the work at the hardware level, z/VM creates separate virtual environments using software. It is highly efficient and it is sometimes used to run large numbers of separate and independent Linux hosts, all within a single LPAR.

Figure 1. HiperSockets usage example

HiperSockets with CHPID FC
This HiperSockets channel path exclusively serves three Linux systems running in LPAR-2, LPAR-3, and LPAR- 4.
HiperSockets with CHPID FD
Connected to this HiperSockets channel path are all servers in the mainframe CPC, which are:
- The multiple Linux servers running under z/VM in LPAR-1
- The z/VM TCP/IP stack running in LPAR-1
- The three Linux servers in LPARs 2 to 4
- All z/OS servers in sysplex A (LPARs 5 to 7) for non-sysplex traffic
- All z/OS servers in sysplex B (LPARs 8 to 10) for non-sysplex traffic
HiperSockets with CHPID FE
This is the connection used by sysplex A (LPARs 5 to 7) to transport TCP/IP user-data traffic among the three sysplex LPARs.
HiperSockets with CHPID FF
This is the connection used by sysplex B (LPARs 8 to 10) to transport TCP/IP user-data traffic among the three sysplex LPARs.

The CHPID type used for a HiperSockets connection is called IQD.

Note: So how fast is IQDIO? How about transferring data between z/OS and Linux using FTP? First, multiple FTP connections must be run in order to get close to utilizing the bandwidth of the interface. When transferring data between a z/OS LPAR and a Linux LPAR over IQDIO, 50 FTP connections produced a total throughput of 600 MBps.

The limitation here, however is not z/OS. In order to increase the throughput, the Linux limitation needs to be overcome. The test was expanded to FTP connections between a single z/OS LPAR and 4 separate Linux LPARs. With 120 total FTP connections (30 for each Linux LPAR), the IQDIO throughput was over 1200 MBps, or more than 1.2 GBps.