You need to ensure that your system meets the
requirements to use SMC-R with RoCE Express® features
operating in a shared RoCE environment.
To use Shared Memory Communications over RDMA
(SMC-R) with RoCE Express features
operating in a shared RoCE environment, the minimum software requirement
must be z/OS® Version 2 Release
1 with APARs OA44576 and PI12223 applied.
SMC-R requires RDMA
over Converged Ethernet (RoCE) hardware and firmware support. The
following minimum hardware requirements must be met to use SMC-R:
- You must have IBM® z13 (z13)
or later systems.
- You must have one or more IBM 10GbE
RoCE Express features.
10GbE
RoCE Express features are
dual ports with short range (SR) optics and can be shared across multiple
operating systems images or TCP/IP stacks in a central processor complex
(CPC).
- You must have System z® OSA-Express
for traditional Ethernet LAN connectivity.
SMC-R does not impose
any specific OSA requirements.
- You must have standard 10 GbE switches.
RoCE network configuration requirements
z/OS Communications Server supports
connectivity to multiple, distinct layer 2 networks through unique
physical LANs. Each unique physical network is identified by existing
Ethernet standards that are based on the physical layer 2 broadcast
domain. You can define a physical network ID (PNet ID) for each physical
network. For more information, see Physical network considerations.
For hosts to communicate by using SMC-R,
they must connect directly to the same Ethernet layer 2 LAN network.
If VLANs are in use, each host must also have access to the same VLAN.
For more information, see VLANID considerations.
There
are restrictions on the physical distances that can be used to route
RDMA frames. To understand these distance specifications and limitations,
see IBM z Systems Planning for Fiber Optic Links.
RoCE network high availability
Because
RoCE connections do not use IP routing and the RDMA connections to
remote hosts are direct point-to-point connections that use reliable
connected queue pairs (RC QPs), there is no concept of an alternative
IP route to the peer. SMC-R connectivity is possible with a single
10GbE RoCE Express feature,
but a loss in that single feature means that the associated TCP connections
and workloads are disrupted. Therefore, redundant 10GbE RoCE Express features on both the
local and remote hosts are required to achieve network high availability
with SMC-R. If your TCP workloads require high availability, redundant
10GbE RoCE Express features
and redundant Ethernet switches are required. The SMC-R protocol actively
uses both features, rather than using one feature with the other in
standby mode. For more information, see High availability considerations.
IBM 10GbE
RoCE Express features also
have redundant internal PCIe support structures, or PCIe internal
paths, as described in Redundancy levels. To avoid another single point
of failure, install each 10GbE RoCE Express feature
that is managed by the same operating system with a unique internal
path. For more information about how to install a 10GbE RoCE Express feature to achieve full
redundancy, see your IBM service representative.
RoCE bandwidth
The 10GbE RoCE Express features provide 10 GbE ports. When
redundant features are defined, SMC-R link groups can be formed by
using both features, resulting in a 20 GbE logical pipe to each physical
network. z/OS Communications
Server uses only two features within a link group at any particular
time.