Datacentre Support Reference Guides

EMC: Enterprise Storage Network Fabric Topology Math

 
 

 

EMC recommends no more than four connectrix switches per fabric based on the following formulae:

One Switch Two Switch
32 Total ports 64 Total ports
- 4 ports reserved for card failure - 4 ports reserved for card failure
28 ports remaining. - 4 ports reserved for E_ports
- (int(28/5)) No more than 4:1 ratio, hosts : fa 56 ports remaining.
23 Possible host connections - (int(56/5)) No more than 4:1 ratio, hosts : fa
/ 2 to support multi-pathing 45 Possible host connections
11 total host connections / 2 to support multi-pathing
22 host connections (gain of 11)
Three switches Four switches
96 total ports 128 total ports
- 4 ports reserved for card failure - 4 ports reserved for card failure
- 12 ports reserved for E_ports - 24 ports reserved for E_ports
80 ports remaining 100 ports remaining
- (int(80/5)) No more than 4:1 ratio, hosts : fa - (int(100/5)) No more than 4:1 ratio, hosts : fa
64 Possible host connections 80 Possible host connections
/ 2 to support multi-pathing / 2 to support multi-pathing
32 host connections (gain of 10) 40 host connections (gain of 8)

Putting in that fourth connectrix means that you gain only 8 host connections from a 32 port connectrix switch. At EMC prices, that's going to be a hard sell to the resident bean counters