Hp XP P9500 Storage Manuel d'utilisateur télécharger pdf (Page 20)

3. Create the pair.

Planning external paths and path groups

The external path is the physical link from the local storage system port to the external storage

system port. You prepare the ports on the local and external systems and then set up the external

path prior to mapping your external volumes.

To prepare and set up ports, see the following sections:

• “Setting up ports on the local system” (page 29)

• “Setting up ports on the external system” (page 30)

External paths

A path consists of cables and possibly switches. You configure your path according to bandwidth

considerations, which include distance, speed, and performance requirements.

Because workload can spike and cable or switch failures can occur, HP strongly recommends that

you set up redundant external paths. A maximum of eight paths can be used per mapped external

volume. Multiple paths—redundancy—allows you to perform I/O operations with external volumes

regardless of workload and/or path failure.

With multiple paths, the external storage system determines how they are used: some systems use

one primary path with alternates available as backups (Single path mode); other systems allow all

paths to be used at the same time, distributing I/O among them (Multi path mode). The path storage

system’s mode cannot be changed. With both modes, you place the paths in path groups and

prioritize each path.

Single path mode

For Single path mode, the external path with the highest priority (primary path) is used to execute

I/O to the external volume. If the primary path cannot be used, it is switched to an alternative

path, after a 3-minute period.

NOTE: The 3-minute interval (the default) is configurable and may not always be 3 minutes.

The following figure illustrates how failure is handled with redundant paths in Single path mode.

20 Requirements and planning

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Hp XP P9500 Storage Manuel d'utilisateur Page 20