IBM ServeRAID M5025, User Manual

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Benefits of the SAS Interface 1-7
1.4.1 Number of Physical Disks Supported
Your configuration planning for the ServeRAID M5025 controller depends
in part on the number of physical disks that you want to use in a RAID
array. The number of drives in an array determines the RAID levels that
can be supported by this controller. Only one RAID level can be assigned
to each virtual disk.
Table 1.1 shows the minimum number and the
maximum number of drives required for each RAID level.
1.5 Benefits of the SAS Interface
SAS is a serial, point-to-point, enterprise-level device interface that
leverages the proven SCSI protocol set. SAS combines the advantages
of SATA II, SCSI, and Fibre Channel, and is the future mainstay of the
enterprise and high-end workstation storage markets. SAS offers a
higher bandwidth per pin than parallel SCSI, and it improves signal and
data integrity.
The SAS interface uses the proven SCSI command set to ensure reliable
data transfers, while providing the connectivity and flexibility of
point-to-point serial data transfers. The serial transmission of SCSI
commands eliminates clock-skew challenges. The SAS interface
provides improved performance, simplified cabling, smaller connectors,
lower pin count, and lower power requirements when compared to
parallel SCSI.
Table 1.1 Physical Devices Required for Each RAID Level
RAID
Level
Minimum # of
Physical Devices
Maximum # of
Physical Devices
0 1 32
1 2 2
5 3 32
6 3 32
10 4 32
50 6 32
60 6 32