SAN Design: March 29, 2001 3:18 pm
Three Tier designs in general allow for higher port count fabrics over Star designs (using the same switch building blocks) but can add additional hops to the design. A middle (core) set of switches can be used to provide connectivity between an upper and lower level of switches. These designs are generally used when data traffic flows between devices attached to the top tier and devices on the bottom tier. For example, hosts on the top tier and storage systems on the bottom. These kinds of connections will have minimal hop counts and also multiple equal cost paths in the fabric to allow for load sharing. If devices at a given level need to communicate via the fabric, there may be additional hops and less variety of paths for this communication. A sample of an acceptable tested three tier design is shown in Figure 10. This particular design was used in Brocade’s Fabric Aware test program to validate heterogeneous device connectivity in a large SAN net- work.
FIGURE 13. Three Tier Design used in Fabric Aware Testing at Brocade
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
A11
A12
A13
A14
B1
B2
B3
B4
C1
C2
C3
C4
C5
C6
Total of 268 ports available
There are a number of possible three tier designs that will work and that are generally in the 200 port count range. Shown in Figure 11 is another example of an operating three tier design. This design includes an extended fabric link via DWDM allowing for connection of two smaller SANs into a large SAN across a dark fiber link using DWDM equipment.
BROCADE Technical Note | Page: 17 of 31 |
