FW 05.01.00 and SW 07.01.00 HP StorageWorks SAN High Availability Planning Guide (AA-RS2DC-TE, June 2003)

Planning Considerations for Fibre Channel Topologies
91SAN High Availability Planning Guide
Ring Fabric
A ring fabric consists of a continuous string of directors or switches connected by
one or more ISLs. Each fabric element is connected to the next fabric element
(like a cascaded fabric, but with the end-point fabric elements connected).
Figure 37 illustrates a ring fabric topology.
Figure 37: Ring fabric
Ring fabrics are generally more expensive than cascaded fabrics, are also easy to
deploy, provide a simple solution to add additional fabric devices, and can solve
hop-count problems inherent to cascaded fabrics. Ring fabrics also have increased
reliability because traffic can route around a single ISL, director, or switch failure
(subject to hop count limitations).
Like cascaded fabrics, ring fabrics are well suited for applications where data
access is local, but not for applications that require any-to-any connectivity. In
addition, ring fabrics are useful when connecting SANs over a MAN or WAN.
These networks typically use a ring topology.
TM
TM
TM
TM
TM
E
R
R
PW
R
R
S
T
1
0
/
1
0
0
T
M
E
R
R
P
W
R
R
ST
1
0
/
1
0
0
T
M
P
W
R
E
R
R
1
0
2
4
6
8
1
0
1
2
1
4
1
6
1
8
2
0
2
2
2
4
2
6
2
8
3
0
3
5
7
9
11
1
3
1
5
1
7
1
9
2
1
2
3
2
5
2
7
2
9
3
1
R
S
T
1
0
/
1
0
0
T
M
Interswitch Link
Fabric Connection