Drive Enclosure Strings

A string is a collection of Drive Enclosures that are connected by a common cable to the same SAS HBA port on both Controller nodes. A string consists of one to five Drive Enclosures. Drive Enclosures are assigned to strings at the factory.

An Oracle FS System with two SAS HBAs installed can have one or two strings to support a maximum of 10 Drive Enclosures. A system with four SAS HBAs can have up to four strings to support a maximum of 20 Drive Enclosures. A performance system can have up to six strings to support a maximum of 30 Drive Enclosures.

The SAS cables connect from the Controller SAS HBA ports to the first Drive Enclosure and the third Drive Enclosure in a string. For small systems with less than three Drive Enclosures, the SAS cables connect from the Controller SAS HBA ports to the first Drive Enclosure and to the last Drive Enclosure in a string.

The following example shows the SAS cable connections for the first string configured in the system with five Drive Enclosures.

Figure 1: The first string with five Drive Enclosures

  

Legend

1 SAS HBA port 0 on Controller 1 and Controller 2

2 Drive Enclosure 3 (I/O module 1, port 0) in the first string and SAS HBA port 0 on Controller 2

3 Drive Enclosure 1 (I/O module 0, port 0) in the first string and SAS HBA port 0 on Controller 1

Each Drive Enclosure is assigned sequentially to the strings, one string at a time. The sequence of assigning strings is based on the performance capabilities of the drives installed in the Drive Enclosures. For optimal performance, the Drive Enclosures with the highest performance drives are first assigned to strings and then continue sequentially until all of the Drive Enclosures are assigned to strings.