IBM Midrange System DS4000 Series Hardware Manual page 131

Figure 4-6 shows an example of enclosure loss protection. If enclosure number 2 fails, the
array with the enclosure loss protection would still function (in a degraded state), as the other
drives are not affected by the failure.
Figure 4-6 Enclosure loss protection
In the example shown in Figure 4-7, without enclosure loss protection, if enclosure number 2
fails, the entire array becomes inaccessible.
Figure 4-7 Array without enclosure loss protection
Best practice: Plan to use enclosure loss protection for your arrays.
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Chapter 4. IBM System Storage DS planning and configuration