SAN Boot Implementation and Best Practices Guide ... - IBM Redbooks

Draft Document for Review June 27, 2012 9:05 am SG247958-Introduction to SAN Boot-CL.fm
problems trying to communicating to the SAN. Multipathing takes advantage of multiple paths
between a host system and the storage subsystems (LUN) or set of LUNs, as shown in
Figure 1-1. When an adapter fails, the system automatically reroutes I/O operations to
another available path. This support also allows the balancing of the I/O load in multiple
paths, preventing I/O bottlenecks.
Figure 1-1 demonstrates why multipath support is necessary. There are a number of single
points of failure between the server bus and the first switch port. Beyond the switch port, there
can be redundancy in both the fabric and the storage subsystem. Without multipathing, the
internal bus cannot reroute I/O from a failed adapter.
xSeries 3755
Internal Bus
Figure 1-1 Possible failure points without multipathing
1.5 What is Switch Zoning
Single points of failure
IBM Switches
IBM DS5300 Controller
Possible redundant paths
Zoning is mandatory when connecting FC hosts to an Storage System via a Fiber Channel
switch. By default most FC switches come with (1) zone preconfigured. Zoning is configured
on the SAN switch, and its purpose is to be boundary isolating and to restrict FC traffic to only
those HBAs within a given zone.
A zone can be either a hard zone or a soft zone. Hard zones group HBAs depending on the
physical ports they are connected to on the SAN switches. Soft zones group HBAs depending
on the World Wide Port Names (WWPNs) of the HBA. Each method has its merits and you
will have to determine which is right for your environment.
Typically, you can use zones to do the following tasks:
► Provide security: Use zones to provide controlled access to fabric segments and to
establish barriers between operating environments. For example, isolate systems with
various uses or protect systems in a heterogeneous environment.
► Customize environments: Use zones to create logical subsets of the fabric to
accommodate closed user groups or to create functional areas within the fabric. For
example, include selected devices within a zone for the exclusive use of zone members, or
create separate test or maintenance areas within the fabric.
► Optimize IT resources: Use zones to consolidate equipment logically for IT efficiency, or to
facilitate time-sensitive functions. For example, create a temporary zone to back up
non-member devices.
The diagram in Figure 1-2 shows a brief overview of a basic zoning configuration.
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Chapter 1. Introduction to SAN Boot 7
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