.Part 1 Architecture HP SAN Design Reference Guide 785351-001

Table 8 Calculating for data availability levels
Number of available portsHardware costFabric design
# ports = n – number of ISL ports
2
x
1
Level 1: single connectivity fabric
# ports = n – number of ISL portsx + additional ISLsLevel 2: single resilient fabric
# ports = n – number of ISL ports –
additional HBA ports
3
x + additional ISLs + additional HBAs
Level 3: single resilient fabric with
multiple device paths
# ports = 2n – number of ISL ports –
additional HBA ports
x + additional ISLs + additional HBAs
+ additional switches
Level 4: multiple fabrics and device
paths (NSPOF)
1
x is the cost of a single connectivity fabric.
2
n is the total number of ports for servers and storage systems.
3
May require use of zoning to define a minimum of two data paths in a single fabric (operating system dependent).
Topology migration
To increase SAN connectivity and capacity:
• Increase the number of switches.
• Use switches with more ports.
• Implement multiple fabrics.
• Implement Fibre Channel routing.
• Migrate to another fabric topology.
• Deploy multiple independent SANs.
Nondisruptive migration
If you have a level 4 multiple fabric NSPOF SAN, you can fail over all operations to one fabric
and then reconfigure the other fabric.
When planning a migration, try to avoid or minimize the movement of devices between switches.
Migrations that require the addition or re-cabling of ISLs are less disruptive than migrations that
require movement of device connections.
Migrating a cascaded fabric SAN
This section describes migration paths for a cascaded fabric SAN.
Cascaded to meshed
To create a meshed fabric SAN, you need additional ISLs to connect all switches. To ensure a
successful migration, calculate the number of ports needed for the additional ISLs. You may need
to move device connections to another switch to make ports available for ISLs.
Cascaded to ring
If you have a linear cascaded fabric SAN, connect the last switch in the fabric to the first switch
to create a ring fabric SAN. If you have a tree-like cascaded fabric SAN (with multiple levels), you
may need to re-cable the ISLs.
Cascaded to core-edge
Determine which switches will be the backbone switches and which ones will be the edge switches.
Re-cable the ISLs to connect all edge switches to the core switches. Connect devices (servers and
storage) or core switches, as required. This migration is less disruptive if you use the existing
switches as edge switches and add switches as core switches.
Topology migration 41