print servers? Does this disk array support any software system that must be available 24 hours per day? Will the information stored in this disk array contain large audio or video files that must be available on demand? Will this disk array contain data from an imaging system? You must identify the purpose of the data to be stored in the disk subsystem before you can confidently choose a RAID level and a RAID configuration.

5.5Planning the Array Configuration

Fill out Table 5.8 to help plan this array.

Table 5.8 Factors for Planning the Array Configuration

Question

Answer

Number of physical disk drives in the array

Purpose of this array. Rank the following factors:

Maximize drive capacity

Maximize the safety of the data (fault tolerance)

Maximize hard drive performance and throughput

Number of hot spares

Amount of cache memory installed on MegaRAID SCSI 320-0

Are all of the disk drives and the server protected by a UPS?

5.5.1Using the Array Configuration Planner

The following table lists the possible RAID levels, fault tolerance, and effective capacity for all possible drive configurations for an array consisting of one to eight drives. This table does not take into account any hot spare (standby) drives. You should always have a hot spare drive in case of drive failure. RAID 1 requires two drives, RAID 10 at least four, and RAID 50 at least six.

Planning the Array Configuration

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