Device Fan-Out Ratio; Device Fan-Out Ratio - HP 316095-B21 - StorageWorks Edge Switch 2/24 Planning Manual

When designing a core-to-edge fabric, servers and storage devices that support
such bandwidth-intensive applications should be attached to core directors as Tier
1 devices. As a best practices policy (assuming 1.0625 Gbps ISLs), devices that
generate a sustained output of 35 MBps or higher are candidates for Tier 1
connectivity. IBM FICON devices also must use Tier 1 connectivity. For
additional information, refer to

Device Fan-Out Ratio

The output of most host devices is bursty in nature; most devices do not sustain
full-bandwidth output, and it is uncommon for the output of multiple devices to
peak simultaneously. These variations are why multiple hosts can be serviced by a
single storage port. This device sharing leads to the concept of fan-out ratio.
Device fan-out ratio is defined as the storage or array port IOPS divided by the
attached host IOPS, rounded down to the nearest whole number. A more
simplistic definition for device fan out is the ratio of host ports to a single storage
port. Fan-out ratios are typically device dependent. In general, the maximum
device fan-out ratio supported is 12 to 1.
to 1.
Device Fan-Out Ratio: 10 to 1
Figure 43: Device fan-out ratio
SAN High Availability Planning Guide
10,000 IOPS
Interswitch Link
Fabric Connection
Planning Considerations for Fibre Channel Topologies
"FCP and FICON in a Single
Figure 43 illustrates a fan-out ratio of 10
1,000 IOPS
1,000 IOPS
1,000 IOPS
1,000 IOPS
1,000 IOPS
Fabric" on page 110.
1,000 IOPS
1,000 IOPS
1,000 IOPS
1,000 IOPS
1,000 IOPS
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