Chapter 5. Host attachment 153
Figure 5-6 Example of a Storage Area Network
Notice in Figure 5-6 how many different types of servers there are sharing the same DS6000
storage and tape library.
5.5.3 SAN cabling for availability and performance
For availability you need to connect to both controllers of the DS6000. If using a switched
fabric, multiple Fibre Channel switches or directors should also be used to avoid the potential
single point of failure. InterSwitch Links (ISLs) can also be used for connectivity.
For performance, a general rule of thumb for host adapters ports is that you have a pair of
host adapter ports connected to the SAN to support each peak throughput increment of
300-400 MB per second for large block sequential workloads. For small block random
workloads a pair of host adapter ports for each increment of 15000 I/Os per second. For a
configuration that is expected to deliver 500MB per second of large block sequential or 40000
IOPS of small block random work, for instance, you should plan to provide at least four
DS6000 host adapter ports into the SAN.
5.5.4 Importance of establishing zones
For Fibre Channel attachments in a SAN, it is important to establish zones to prevent
interaction from host adapters. Every time a host adapter joins the fabric, it issues a
SAN
Storage Area Network
san switches
Tape Library
DS6000
disk storage
SUN host
AIX host
HP-UX host
Windows 2003
Windows 2000
Fibre Channel
SAN Volume
Controller
Linux host

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