5 Configuring MegaRAID

Configuring SCSI Physical Drives

SCSI Channels Physical SCSI drives must be organized into logical drives. The arrays and logical drives that you construct must be able to support the RAID level that you select.

Your MegaRAID adapter has four SCSI channels.

Distributing Drives Distribute the disk drives across all channels for optimal performance. It is best to stripe across channels instead of down channels. Performance is most affected for sequential reads and writes. MegaRAID supports SCSI CD-ROM drives, SCSI tape drives, and other SCSI devices as well as SCSI hard disk drives. For optimal performance, all non-disk SCSI devices should be attached to one SCSI channel.

Basic Configuration Rules You should observe the following guidelines when connecting and configuring SCSI devices in a RAID array:

•attach non-disk SCSI devices to a single SCSI channel that does not have any disk drives

•distribute the SCSI hard disk drives equally among all available SCSI channels except any SCSI channel that is being reserved for non-disk drives

•you can place up to 32 physical disk drives in a logical array, depending on the RAID level

•an array can contain SCSI devices that reside on an array on any channel

•include all drives that have the same capacity to the same array

•make sure any hot spare has a capacity that is at least as large as the largest drive that may be replaced by the hot spare

•when replacing a failed drive, make sure that the replacement drive has a capacity that is at least as large as the drive being replaced

Chapter 5 Configuring MegaRAID

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