Technical information

June 2012 Dell EqualLogic Configuration Guide v13.2 58
be interconnected. Since the IO modules are not interconnected via the chassis midplane, the
only alternative is to use external ports (stacking or Ethernet) to make these inter-switch
connections.
• Maximum stack size versus practical stack size
• Depending on the IO module model, the maximum number of switches allowed in a single
stack may be different. In addition, the number of switches supported by the switch may not
be optimal for a SAN using EqualLogic arrays. SAN solutions tend to be sensitive to latency
and adding multiple hops between a host and target may create situations where latency
becomes unacceptable for your application. Testing is advised.
• Each M1000e enclosure will contribute two switches to the stack placing an upward limit on
the number of enclosures that can be interconnected into a single SAN network. Regardless
of the maximum number of IO modules supported in a single stack, Dell recommends not
going above six switches in the stack due to possible hop related latency.
• M-Series IO Module Stacking Compatibility
• Not all M-Series IO modules can be stacked together or with external switches. Typically,
each M-Series IO modules model can only stack with modules of the same exact model. It
may also be possible to stack M-Series IO modules with some “stack compatible” stand-alone
PowerConnect switch models. The table below provides stack compatibility information.
Table 24 Stack Compatibility for M-Series IO Modules
Stack Compatible Switches
Maximum
Stack Size
Recommended
Stack Size
PowerConnect M6220
PowerConnect M6220
PowerConnect 6224
PowerConnect 6248
10 4
PowerConnect M6348
PowerConnect M6348
PowerConnect 7024
PowerConnect 7048
12 6
PowerConnect M8428-k N/A N/A N/A
PowerConnect M8024-k
M8024-k
PowerConnect 8024
PowerConnect 8024F
6 6
Cisco Catalyst Blade Switch 3032 N/A N/A N/A
Cisco Catalyst Blade Switch 3130G
Catalyst BS3130G
Catalyst BS3130X
8 4
Cisco Catalyst Blade Switch 3130X
Catalyst BS3130G
Catalyst BS3130X
8 4
4.7.1.1 SAN Design for a Single M1000e Enclosure
For a single M1000e enclosure, there is a requirement to use two blade IO modules for redundancy.
Depending on the blade IO module model, you may use either stacking or link aggregation as
described earlier in Table 23. Where stacking is supported, this will most likely be the primary method
of interconnecting the blade IO modules to create a single switch fabric. SAN switches can be located
in any of the three enclosure fabrics and it is not required that the blade IO modules be in the same
enclosure fabric, though it is typical that the two IO modules would be in the same enclosure fabric.