# Guidelines and Limitations

To design CFS regions for FC-Redirect, follow these guidelines:

• Ensure the CFS region configuration for FC-Redirect can be applied to all FC-Redirect-based applications. The applications include SME, Cisco DMM, and any future applications.

• Ensure that all FC-Redirect-capable switches that are connected to the hosts, targets, and the application switches (switches with MSM-18/4 modules in a cluster) are configured in the same region.

• If there are multiple SME clusters in a region, a target can be part of the SME configuration in only one cluster. To change the target to a different cluster, the configuration in the first cluster must be deleted before creating the configuration in the second cluster.

• All switches in the region must have a common VSAN.

• For existing SME installations, refer to “Configuring CFS Regions For FC-Redirect” for steps on migrating to CFS regions.

• Remove all instances of the previous configurations when a switch is moved to a region or moved out of a region.

To configure a CFS region, refer to the “Configuring CFS Regions For FC-Redirect”.

Table 1-2 lists the SME configurations and the corresponding limits.

Table 1-2 SME Tape Configuration Limits

Configuration | Limit
Number of clusters per switch | 1
Switches in a cluster | 4
Number of fc-redirect capable switches in a fabric | 10
Fabrics in a cluster | 2
Modules in a switch | 11
Cisco MSM-18/4 modules in a cluster | 32
Initiator-Target-LUNs (ITLs) | 1024
LUNs behind a target | 32
Host and target ports in a cluster | 128
Number of hosts per target | 128
Tape backup groups per cluster | 4
Volume groups in a tape backup group | 32
Keys in a Tape volume group | 8000
Number of disk groups | 128
Number of SME disks (LUNs) | 2000
Cisco Key Management Center (number of keys) | 32,000
Targets per switch that can be FC-redirected | 32
IT connections per SME interface (soft limit) | 256 Note Beyond this limit, a syslog message will be displayed. It is recommended that you provision more SME interfaces in the cluster.1
IT connections per SME interface (hard limit) | 512 Note Beyond this limit, new IT connections will not be assigned to that particular SME interface and a critical syslog will be displayed.2

Table 1-3 SME Disk Configuration Limits

Configuration | Per Cluster | Per Switch | Per Crypto Node
Number of clusters | NA | 2 | 1
Number of physical fabrics | 2 | NA | NA
Number of switches | 8 | NA | NA
Number of modules (line cards—SSN 16 or MSM-18/4 modules) | NA | 11 | NA
Cisco SME interfaces (crypto nodes used for encryption) | 32 | 32 | NA
Initiator-Target-LUNs (ITLs) | 2048 | 2048 | 512
LUNs behind a target | 512 | 512 | 512
Number of initiator ports | 128 | NA | NA
Number of target ports | 128 | NA | NA
Maximum number of IT nexus | 128 | NA | NA
Number of paths per LUN (physical paths per SME disk) | 8 | 8 | 8
Number of disk groups | 128 | 128 | 128
Number of SME disks (LUNs) | 2048 | 2048 | 512
Cisco Key Management Center (KMC) number of keys | 32,000 | 32,000 | 32,000
Maximum number of concurrent data preparations (offline data preparations) | NA | NA | 64
Total number of Disk key replication relationships | 2048

NA—Not applicable

1. Applicable from NX-OS Release 4.2(1) and later
2. Applicable from NX-OS Release 4.2(1) and later