Configuring the raid controller, Configuring scsi physical drives – Dell PERC 4/DC User Manual
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Configuring the RAID Controller
Dell™ PowerEdge™ Expandable RAID Controller 4/SC, 4/DC, and 4e/DC User's Guide
Configuring SCSI Physical Drives
Planning the Array Configuration
This section describes how to configure for physical drives, arrays, and logical drives. It contains tables you can complete to list the configuration for the
physical drives and logical drives.
Configuring SCSI Physical Drives
Your SCSI hard drives must be organized into logical drives in an array and must be able to support the RAID level that you select.
Observe the following guidelines when connecting and configuring SCSI devices in a RAID array:
l
You can place up to 28 physical drives in an array.
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Use drives of the same size and speed to maximize the effectiveness of the controller.
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When replacing a failed drive in a redundant array, make sure that the replacement drive has the same or larger capacity than the smallest drive in the
array (RAID 1, 5, 10, and 50).
When implementing RAID 1 or RAID 5, disk space is spanned to create the stripes and mirrors. The span size can vary to accommodate the different disk sizes.
There is, however, the possibility that a portion of the largest disk in the array will be unusable, resulting in wasted disk space. For example, consider a RAID 1
array that has the following disks, as shown in
.
Table 4-1. Storage Space in a RAID 1 Array
In this example, data is mirrored across the two disks until 20 GB on Disk A and B are completely full. This leaves 10 GB of disk space on Disk B. Data cannot be
written to this remaining disk space, as there is no corresponding disk space available in the array to create redundant data.
provides an example of a RAID 5 array.
Table 4-2. Storage Space in a RAID 5 Array
NOTE:
For RAID levels 10 and 50, the additional space in larger arrays can store data, so you can use arrays of different sizes.
Disk Disk Size Storage Space Used in Logical Drive for RAID 1 Array Storage Space Left Unused
A
20 GB
20 GB
0
B
30 GB
20 GB
10 GB
Disk Disk Size Storage Space Used in Logical Drive for RAID 5 Array Storage Space Left Unused
A
40 GB
40 GB
0 GB
B
40 GB
40 GB
0 GB
C
60 GB
40 GB
20 GB