IBM DS3500, Введение и руководство по внедрению

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Chapter 3. IBM System Storage DS3500 Storage System planning tasks
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Draft Document for Review March 28, 2011 12:24 pm
7914DS3KPlanning_090710.fm
The same rules apply to 8 Gbps devices relative to 4 Gbps and 2 Gbps environments. The
8 Gbps devices have the ability to automatically negotiate back down to either 4 Gbps or 2
Gbps, depending upon the attached device and the link quality. A 4 Gbps device has the
ability to automatically negotiate back down to either 2 Gbps or 1Gbps. If the link does
unexpectedly negotiate to a slower speed than expected, then the causes or reasons for this
ought to be investigated and remedied.
The DS3500 Storage System now has 8 Gbps functionality; there are several switches and
directors that operate at this speed.
FC host attachment methods
With FC SAN environments there are two methods of host attachment to the storage system
that are commonly used; direct-attached and switch-attached (fabric).
Direct-attached DS3500
Figure 3-8 shows a simple direct-attached configuration. Two host servers are connected to a
dual-controller DS3500. Each server uses two FC HBAs, so this is a fully redundant setup. If
an HBA, FC cable, or RAID controller fails, the host servers will still have access to logical
drives. This type of setup is suitable for a two-node Microsoft Cluster Server configuration.
Figure 3-8 Host servers attached to DS3500 FC direct connect
Note: On certain fiber switch vendor models, it might be necessary to configure the port to
a specific speed of 2, 4, or 8 Gbps to obtain the required speed instead of leaving
“auto-detection” on the port.