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This chapter provides an overview of the Cisco I/O Accelerator feature and includes the following sections:
The Cisco MDS 9000 Family I/O Accelerator (IOA) feature provides Small Computer System Interface (SCSI) acceleration in a storage area network (SAN) where the sites are interconnected over long distances using Fibre Channel or Fibre Channel over IP (FCIP) Inter-Switch Links (ISLs).
IOA provides these features, which are described in the following sections:
IOA provides both SCSI write acceleration and tape acceleration features as a unified fabric service. These services were provided in previous releases in the form of Fibre Channel write acceleration for remote replication over Fibre Channel links and FCIP write acceleration and tape acceleration over FCIP links. Fibre Channel write acceleration was offered on the Storage Services Module (SSM) and FCIP write acceleration and tape acceleration were offered on the IP storage services modules. IOA offers both the write acceleration and tape acceleration services on the Cisco MDS MSM-18/4 module, SSN-16 module, and 9222i switch as a fabric service. This eliminates the need to buy separate hardware to obtain Fibre Channel write acceleration and FCIP write acceleration and tape acceleration.
IOA can be deployed anywhere in the fabric without rewiring the hardware or reconfiguring the fabric. There are no restrictions on where the hosts and targets are connected to. Both the Fibre Channel and FCIP write acceleration is supported only on PortChannels but do not support multiple equal-cost links. FCIP tape acceleration is not supported on PortChannels. IOA eliminates these topological restrictions.
IOA is completely transport-agnostic and is supported on both Fibre Channel and FCIP ISLs between two sites.
IOA equally supports both PortChannels and equal-cost multiple path (ECMP) links across two data centers. This allows you to seamlessly add ISLs across the two data centers for capacity building or redundancy. IOA is completely resilient against ISL failures. IOA uses a Lightweight Reliable Transport Protocol (LRTP) to guard against any ISL failures as long as there is an alternate path available across the two data centers. Remote replication and tape backup applications are completely unaffected by these failures.
IOA tape acceleration provides higher throughput numbers than the FCIP tape acceleration, which is limited by a single Gigabit Ethernet throughput.
IOA uses clustering technology to provide automatic load balancing and redundancy for traffic flows across multiple IOA service engines that can be configured for the IOA service. When an IOA service engine fails, the affected traffic flows are automatically redirected to the available IOA service engines to resume acceleration.
Figure 1 illustrates a physical fabric that consists of two sites in different locations interconnected across the MAN or WAN using Fibre Channel or FCIP links. Remote replication and remote tape backup services run across these two data centers.
Note | This topology illustrates a single fabric only. In a dual fabric, the second fabric is an exact replica of this topology, and the concepts that are described in this document are applicable to the second fabric as well. |
The following Cisco IOA-related terms are used in this book:
Note | When using the CLI, only the switches where IOA is deployed need to be classified into a site. When using the Cisco DCNM-SAN, all the switches in a physical location need to be classified into a site. The site classification is used internally by the Cisco DCNM-SAN to automate the classification of the flows that traverse across sites. |
An IOA interface must be brought up administratively to enable the IOA service on the service engine.
Both the host and the target or tape must be directly attached to a FC-Redirect-capable switch.
IOA provide bidirectional acceleration for each configured flow. A separate reverse flow configuration is not required.
Note | You can have more than one IOA service engine in the same site in the IOA cluster. This is the preferred configuration when an IOA service engine fails, then all the flows bound to it can be automatically moved to another available IOA service engine in the same site. This function is taken care of by the IOA cluster based load balancer. |
IOA is offered as a clustered service that consists of a set of switches that operates in coordination with each other. Clustering provides the following advantages:
IOA clustering uses standard algorithms to provide consistency and reliability of the configuration metadata required for the service to be operational. A master switch is internally elected by the clustering infrastructure to perform certain tasks such as load-balancing and failover. To keep the process simple, we recommend that you provision the IOA from the master switch. If the network fails, which partitions the switches in a cluster, a standard majority node-based quorum algorithm is used to decide which partition should be operational to guarantee the consistency.
An internal node ID that is allocated as a part of adding the switches to the cluster is used in the master election algorithm. If you intend to manage IOA from a specific switch or a site, we recommend that you use this switch as a seed switch when a IOA cluster is configured, and also add all the nodes in this site before you add the nodes from the remote site into the IOA cluster.
IOA is supported on the Cisco MDS 9000 Family 18/4-port Multiservice Module MSM-18/4, the Cisco MDS 9222i Switch, the Cisco MDS 9250i Switch, and the 16-Port Storage Services Node (SSN-16) module. Each MSM-18/4 Module, 9222i Switch, and 9250i Switch has one service engine that can be configured for the Cisco IOA service. The SSN-16 module has four service engines that can be used for the IOA service.
IOA scaling with NX-OS release 6.2(3) is supported only on Supervisor 2a module and not supported on Supervisor 2 module.
To enable the IOA feature on the MSM-18/4 Module or SSN-16 Module, the MDS 9000 Family switch must run Cisco NX-OS Release 4.2(1) or later. To enable IOA on the MDS 9250i Switch it should run Cisco NX-OS Release 6.2(5). You must also use Cisco DCNM-SAN 5.2(1) to manage the switches. Hosts must be connected to a switch running Cisco SAN-OS 3.3(1c) or later. Targets must be connected to a switch running Cisco NX-OS Release 4.2(1) or later.
The Cisco MDS 9710 Switch can have Cisco NX-OS Release 6.2(1) or 6.2(3) or above, if the hosts are directly connected to the Cisco MDS 9710 Switch that is participating in the IOA. But if the targets that are participating in IOA are directly connected to it (Cisco MDS 9710 Switch), then we must have Cisco NX-OS release 6.2(3) and above running on that Cisco MDS 9710 Switch.
After the target is connected to the Cisco MDS 9710 Switch with Cisco NX-OS Release 6.2(3) or above, IOA (master/slave) switch should be able to communicate with the Cisco MDS 9710 Switch (targets are connected) with at least one path where all FCR-capable switches are connected in between the IOA (master/slave) and Cisco MDS 9710 Switch.
The Cisco MDS 9000 Family IOA package is licensed per service engine and is tied to the chassis. The number of licenses required is equal to the number of service engines on which the intelligent fabric application is used.
IOA runs on the MDS 9222i Switch (native), MDS 9250i Switch (native) and on the MSM-18/4 Module and SSN-16 Module. The modules are supported in the MDS 9500 Directors and the MDS 9222i Switch.
On the SSN-16 Module, a separate license is required for each engine that will run IOA. Each SSN-16 engine configured for IOA checks out a license from the pool managed at the chassis level. For convenience, SSN-16 Module licenses can be purchased singly (the usual model) or in a package of four. Once they are installed into an MDS 9000 chassis, there is no difference between the IOA package of four and four single IOA licenses.
On the SSN-16 Module, because each engine is licensed independently, different licensed features can be configured on the four engines based on the following requirements for NX-OS Release 4.2(1):
To use the IOA features, Cisco MDS NX-OS Release 4.2(1) or later must be installed on a Cisco MDS 9000 Family switch and Cisco MDS9250i Switch must be running Cisco NX-OS Release 6.2(5).
Table 1 lists the available Cisco IOA licenses.
Part Number |
Description |
Applicable Product |
---|---|---|
M9250IIOA |
Cisco I/O Acceleration License for MDS 9250i. |
MDS 9250i |
M92IOA184 |
Cisco I/O Acceleration License for MSM-18/4 on MDS 9200, spare. |
MSM-18/4 on MDS 9200 |
M95IOA184 |
Cisco I/O Acceleration License for MSM-18/4 on MDS 9500, spare. |
MSM-18/4 on MDS 9500
|
M95IOASSN |
Cisco IOA License (1 engine) for SSN-16 on MDS 9500, spare. |
SSN-16 on MDS 9500 |
M92IOASSN |
Cisco IOA License (1 engine) for SSN-16 on MDS 9200, spare. |
SSN-16 on MDS 9200
|
M95IOASSN4X |
Cisco IOA License (4 engines) for SSN-16 on MDS 9500, spare. |
SSN-16 on MDS 9500
|
M92IOASSN4X |
Cisco IOA License (4 engines) for SSN-16 on MDS 9200, spare. |
SSN-16 on MDS 9200
|
M9222IIOA |
Cisco I/O Accelerator License for MDS 9222i, spare. |
MDS 9222i Switch |
Note | A device is either a switch or a module. When you enter the serial number for the device, make sure that you enter the serial number for the correct device; either the switch or the module for which you want to get the license. You can use the show license host-id command to find out which serial number to lock the license against. |