Specifications

DATA CENTER BEST PRACTICES
SAN Design and Best Practices 45 of 84
fig33_SAN_Design
Gaussian or
“normal”
distribution
f
g
(x)
.00135.00135
.0214.0214
X
0
σ 2 σ 3 σ - σ -2 σ -3 σ
.1359.3413.3413.1359
Figure 32. Gaussian curve.
For remote tape/Virtual Tape Library (VTL) backup, the extension systems can be used to extend the data center
fabric from the location where backup servers are attached to the remote fabric and where the remote tape/VTL
is located, as shown by the blue arrow in Figure 33.
fig34_SAN_Design
Brocade
7800
IP network,
dark ber,
xWDM
Brocade
FX8-24 in
DCX chassis
FC SAN
FC SAN
Hosts
Backup
server
FC SAN
FC SAN
Remote
tape/VTL
Figure 33. SAN extension extending the data center fabric to remote tape or VTL.
It is important that you measure the tape volume in MB/h, as well as the number of tape drives used, and to
determine the batch window in hours. These measurements will determine the amount of network bandwidth
that is required.
You can take advantage of FCIP Trunking to implement redundant network routes from site to site. But it is
important to understand whether trafc can fail over to the alternate route transparently or whether that will
impact trafc ow.
For both disk and tape extension using emulation (FastWrite for disk and Tape Pipelining for tape), a single
tunnel between sites is recommended. If multiple tunnels must be used, use Trafc Isolation (TI) zones or logical
switch conguration to ensure that the same exchange always traverses by the same tunnel in both directions.
Use multiple circuits instead of multiple tunnels for redundancy and failover protection.