Serial-attached SCSI cable planning

Serial-attached SCSI cable planning

Serial-attached SCSI (SAS) cables provide serial communication for transfer of data for directly attached devices, such as hard disk drives, solid-state drives, and CD-ROM drives.

SAS cable overview

Serial-attached SCSI (SAS) is an evolution of the parallel SCSI device interface into a serial point-to-point interface. SAS physical links are a set of four wires used as two differential signal pairs. One differential signal transmits in one direction while the other differential signal transmits in the opposite direction. Data might be transmitted in both directions simultaneously. SAS physical links are contained in ports. A port contains one or more SAS physical links. A port is a wide port if there are more than one SAS physical link in the port. Wide ports are designed to enhance performance and provide redundancy incase an individual SAS physical link fail.

Each SAS cable contains four SAS physical links that are typically organized into either a single 4x SAS port or two 2x SAS ports. Each end of the cable uses a mini SAS 4x connector. Review the following design and installation criteria before installing your SAS cables:

• Only specific cabling configurations are supported. Many configurations could be constructed that are not supported and will either not function correctly or will generate errors. Refer to SAS cabling configurations for diagrams of the supported cabling configurations.
• Each mini-SAS 4x connector is keyed to help prevent cabling an unsupported configuration.
• Each cable end has a label that graphically describes the correct component port to which it is connected, such as:
  • SAS adapter
  • Expansion drawer
  • System external SAS port
  • Internal SAS disk slots connection.
• Cable routing is important. For example, YO, YI, and X cables must be routed along the right side of the rack frame (as viewed from the rear) when connecting to a disk expansion drawer. Additionally, X cables must be attached to the same numbered port on both SAS adapters to which it connects.
• When a choice of cable lengths is available, select the shortest cable that will provide the needed connectivity.
• Always use care when inserting or removing a cable. The cable should slide easily into the connector. Forcing a cable into a connector can cause damage to the cable or connector.
• The X cables are only supported on all SAS PCI (RAID) adapters and only when RAID is enabled.
• Not all cabling configurations are supported when using solid-state drives (SSD). Refer to Installing and configuring Solid State Drives for more information.

Supported SAS cable information

The following table contains a list of the supported SAS cable types and their designed usage.

Table 1. Functions for supported SAS cables

Cable type	Function
AA cable	This cable is used to connect between the top ports on two tri-port SAS adapters in a RAID configuration.
AI cable	This cable is used to connect from a SAS adapter to internal SAS disk slots using an FC3650 or FC3651 cable card or to the System External SAS port on models 8204-E8A (FC3669) or 8203-E4A (FC3670). This cable is also used between the adapter connector and cable card connector on an FC5909 or FC5911 combination adapter and cable card.
AE cable	These cables are used to connect a SAS adapter to a media expansion drawer. These cables can also be used to connect two SAS adapters to a disk expansion drawer in a unique JBOD configuration.
AT cable	This cable is used with a PCIe 12X I/O drawer to connect from a PCIe SAS adapter to the internal SAS disk slots.
EE cable	This cable is used to connect one disk expansion drawer to another in a cascaded configuration. Disk expansion drawers can only be cascaded one level deep, and only in certain configurations.
YO cable	This cable is used to connect a SAS adapter to a disk expansion drawer. It is also used to connect a 9125-F2A system I/O unit to a disk expansion drawer. The cable must be routed along the right side of the rack frame (as viewed from the rear) when connecting to a disk expansion drawer.
YI cable	This cable is used to connect a system external SAS port to a disk expansion drawer. The cable must be routed along the right side of the rack frame (as viewed from the rear) when connecting to a disk expansion drawer.
X cable	This cable is used to connect two SAS adapters to a disk expansion drawer in a RAID configuration. The cable must be routed along the right side of the rack frame (as viewed from the rear) when connecting to a disk expansion drawer.
YR cable	This cable is used to connect two SAS adapters to internal SAS disk slots using an FC3651 cable card.

The following table contains specific information about each supported SAS cable.

Table 2. Supported SAS cables

Name	Length	IBM® part number	Feature code
SAS AA cable	3 m (9.8 ft) 6 m (19.6 ft)	44V8231 44V8230	3681 3682
SAS 4x AI cable	1 m (3.2 ft)	44V4041	3679
SAS 4x AE cable	3 m (9.8 ft)	44V4163	3684
	6 m (19.6 ft)	44V4164	3685
SAS 4x AT cable	0.6 m (1.9 ft)	44V5132	3688
SAS 4x EE cable	1 m (3.2 ft)	44V4147	3652
	3 m (9.8 ft)	44V4148	3653
	6 m (19.6 ft)	44V4149	3654
SAS YO cable	1.5 m (4.9 ft)	44V4157	3691
	3 m (9.8 ft)	44V4158	3692
	6 m (19.6 ft)	44V4159	3693
	15 m (49.2 ft)	44V4160	3694
SAS YI cable	1.5 m (4.9 ft)	44V4161	3686
	3 m (9.8 ft)	44V4162	3687
SAS X cable	3 m (9.8 ft)	44V4154	3661
	6 m (19.6 ft)	44V4155	3662
	15 m (49.2 ft)	44V4156	3663
SAS YR cable	1 m (3.2 ft)	44V4818	3667
Split disk backplane cable card for a 3/3 split 9117-MMA		44V3557	3650
Split disk backplane cable card for a 6/0 split 9117-MMA		44V3435	3651
Disk backplane to rear bulkhead, cascading. (internal cable) 8204-E8A, 9409-M50		42R5751	3668
Split disk backplane to rear bulkhead (internal cable) 8204-E8A		44V5252	3669
Split disk backplane to rear bulkhead (internal cable) 8203-E4A		44V5253	3670
Disk backplane to rear bulkhead, cascading. (internal cable) 8203-E4A, 9408-M25		44V3382	3674

The following table contains cable label information. The graphic labels are designed to match the correct component port to which the cable end is to be attached.

Table 3. SAS cable labeling

Name	Connects	Label
SAS AA cable	Top connectors on tri-port SAS adapter to tri-port SAS adapter.
SAS 4x AI cable	SAS adapter to internal SAS disk slots through an FC3650 or FC3651 cable card or an FC5909 or FC5911 combination adapter and cable card or to the System External SAS port on models 8204-E8A (with FC3669 installed) or 8203-E4A (with FC3670 installed)
SAS 4x AE cable	SAS adapter to a media expansion drawer or two SAS adapters to a disk expansion drawer in a unique JBOD configuration
SAS 4x AT cable	PCIe SAS adapter in PCIe 12X I/O drawer to the internal SAS disk slots
SAS 4x EE cable	One disk expansion drawer to another disk expansion drawer in a cascaded configuration
SAS YO cable	SAS adapter or 9125-F2A system I/O unit to a disk expansion drawer
SAS YI cable	System external SAS port to a disk expansion drawer
SAS X cable	Two SAS adapters to a disk expansion drawer in a RAID configuration
SAS YR cable	Two SAS adapters to internal SAS disk slots through an FC3651 cable card

Cable section lengths

Figure 1. SAS external X cable assembly cable lengths

Figure 2. SAS external YO-cable assembly cable lengths

Figure 3. SAS external YI-cable assembly cable lengths

Figure 4. SAS external YR-cable assembly cable lengths

SAS cabling configurations

The following sections provide the typical supported SAS cabling configurations. Many configurations could be constructed that are not supported and will either not function correctly or will generate errors. To avoid problems, restrict cabling to only the general types of configurations shown in the following sections.

• SAS adapter to disk expansion drawers
• SAS adapter to media expansion drawer
• SAS adapter to expansion drawer combinations
• System external SAS port to disk expansion drawer- models 8204-E8A, 8203-E4A, 9408-M25, and 9409-M50
• System I/O unit external SAS port to disk expansion drawer- model 9125-F2A
• SAS adapter to internal SAS disk slots in models 9117-MMA
• Two SAS adapters to internal SAS disk slots in models 9117-MMA and 9406-MMA
• SAS adapter to internal SAS disk slots in models 8204-E8A and 8203-E4A
• Two SAS adapters to disk expansion drawer multi-initiator high availability (HA) RAID configuration
• Two SAS adapters to disk expansion drawer - multi-initiator HA JBOD configuration
• PCIe SAS adapter in PCIe 12X I/O drawer to the internal SAS disk slots

SAS adapter to disk expansion drawers

Figure 5, Figure 6, Figure 7, and Figure 8 illustrate connecting a SAS adapter to one, two, three, or four disk expansion drawers. It is also possible to connect three disk expansion drawers by omitting one of the cascaded drawers shown in Figure 7. Disk expansion drawers can be cascaded only one level deep.

Figure 5. SAS adapter to a disk expansion drawer

Note: The YO cable must be routed along the right side of the rack frame.

Figure 6. SAS adapter to two disk expansion drawers

Note: The YO cable must be routed along the right side of the rack frame.

Figure 7. SAS adapter to four disk expansion drawers

Note: The YO cable must be routed along the right side of the rack frame.

Figure 8. Tri-port SAS adapter to disk expansion drawers

When attaching only hard disk drives, it is also possible to cascade a second disk expansion drawer off of two out of the three drawers for a maximum of five disk expansion drawers per adapter. Refer to Figure 7. Disk expansion drawers can be cascaded only one level deep.

Note: The YO cable must be routed along the right side of the rack frame.

SAS adapter to media expansion drawer

Figure 9 illustrates connecting a SAS adapter to a media expansion drawer. It is also possible to connect a second media expansion drawer to the second port of the SAS adapter.

Figure 9. SAS adapter to a media expansion drawer

SAS adapter to expansion drawer combinations

Figure 10 illustrates connecting a SAS adapter to both a disk expansion drawer and a media expansion drawer on separate adapter ports. It is also possible to cascade a second disk expansion drawer (refer to Figure 7).

Figure 10. SAS adapter to both a disk expansion drawer and a media expansion drawer

Note: The YO cable must be routed along the right side of the rack frame.

System external SAS port to disk expansion drawer- models 8204-E8A, 8203-E4A, 9408-M25, and 9409-M50

Figure 11 illustrates connecting a system external SAS port to a disk expansion drawer. Disk expansion drawers cannot be cascaded.

Figure 11. System external SAS adapter port to a disk expansion drawer

Note: The YI cable must be routed along the right side of the rack frame.

System I/O unit external SAS port to disk expansion drawer- model 9125-F2A

Figure 12 and Figure 13 illustrate connecting a 9125-F2A system I/O unit external SAS port to one or two disk expansion drawers.

Note: The disk expansion drawers can be cascaded only one level deep.

Figure 12. SAS adapter to a disk expansion drawer

Note: The YO cable must be routed along the right side of the rack frame.

Figure 13. SAS adapter to two disk expansion drawers

Note: The YO cable must be routed along the right side of the rack frame.

SAS adapter to internal SAS disk slots in models 9117-MMA

Figure 14 and Figure 15 illustrate connecting a SAS adapter to internal SAS disk slots through one or two FC3650 or FC3651 cable cards. Figure 17 andFigure 19 illustrate connecting a disk expansion or media expansion drawer in addition to the internal SAS disk slots. Figure 20 illustrates connecting a SAS adapter to internal SAS disk slots through an FC5909 or FC5911 combination adapter and cable card.

Note: When installing Feature Code 3650 or 3651, you might have difficulties inserting and plugging the card assembly. This is caused by an interference of a bracket installed within the enclosure. When this problem is encountered contact IBM for removal of the bracket and installation of the feature at no charge. Removal of this bracket does not affect the functionality of the system.

Figure 14. SAS adapter to internal SAS disk slots through an FC3650 or FC3651 cable card

Figure 15. SAS adapter to internal SAS disk slots through two FC3650 or FC3651 cards

Figure 16. FC5904 or FC5908 adapter connecting to three system units through an FC3650 or FC3651 cable card

Figure 17. SAS adapter to disk expansion drawer and internal SAS disk slots through an FC3650 or FC3651 cable card

Figure 18. FC5904 or FC5908 adapter connecting to the FC3650 or FC3651 in a system unit and connecting to a disk expansion drawer

Figure 19. SAS adapter to media expansion drawer and internal SAS disk slots through an FC3650 or FC3651 cable card

Figure 20. SAS adapter to internal SAS disk slots through an FC5909 or FC5911 combination adapter and cable card.

Note: The middle connector on the FC5909 is not used for any connection. The middle connector on the FC5911 can be used to connect an additional disk expansion or media expansion drawer. Refer to the expansion drawer connection in Figure 17 and Figure 19.

Two SAS adapters to internal SAS disk slots in models 9117-MMA and 9406-MMA

Figure 21 and Figure 22 illustrate connecting two SAS adapters to internal SAS disk slots through one or two FC3651 cable cards.

Figure 21. Two SAS adapters to internal SAS disk slots through an FC3651 cable card

Figure 22. Two SAS adapters to internal SAS disk slots through two FC3651 cable cards

SAS adapter to internal SAS disk slots in models 8204-E8A and 8203-E4A

Figure 23 illustrates connecting a SAS adapter to internal SAS disk slots through the system external SAS port.

Note: Internal cable FC3670 for model 8203-E4A or FC3669 for model 8204-E8A must be installed to enable this configuration. For more information, seeInstalling the external SAS port on a model 8203-E4A, 9407-M15, or 9408-M25 or Installing the external SAS port on a model 8204-E8A or 9409-M50.

Figure 23. SAS adapter to internal SAS disk slots through the system external SAS port

Notes:

• Internal cable FC3670 for model 8203-E4A or FC3669 for model 8204-E8A must be installed to enable this configuration. For more information, seeInstalling the external SAS port on a model 8203-E4A, 9407-M15, or 9408-M25 or Installing the external SAS port on a model 8204-E8A or 9409-M50.
• The second connector on the adapter can be used to attach a disk expansion or media expansion drawer as shown in Figure 5 or Figure 9.

Figure 24. FC5904 or FC5908 adapter attached to disk expansion drawers

Note:

• The remaining two connectors on the adapter can be used to attach disk expansion drawers as shown in Figure 8.

Two SAS adapters to disk expansion drawer multi-initiator high availability (HA) RAID configuration

Figure 25, Figure 26, Figure 27, and Figure 28 illustrate connecting two SAS adapters to one, two, or four disk expansion drawers in a RAID configuration. It is also possible to connect three disk expansion drawers by omitting one of the cascaded drawers shown in Figure 27. Disk expansion drawers can be cascaded only one level deep.

Figure 25. Two SAS RAID adapters to a disk expansion drawer in a multi-initiator HA RAID configuration

Note:

1. The X cable must be routed along the right side of the rack frame.
2. The X cable must be attached to the same numbered port on all adapters.

Figure 26. Two SAS RAID adapters to two disk expansion drawers in a multi-initiator HA RAID configuration

Note:

1. The X cable must be routed along the right side of the rack frame.
2. The X cable must be attached to the same numbered port on all adapters.

Figure 27. Two SAS RAID adapters to four disk expansion drawers in a multi-initiator HA RAID configuration

Note:

1. The X cable must be routed along the right side of the rack frame.
2. The X cable must be attached to the same numbered port on all adapters.

Figure 28. Two Tri-port SAS adapters to disk expansion drawers in a multi-initiator HA raid configuration

When attaching only hard disk drives, it is also possible to cascade a second disk expansion drawer off of two out of the three drawers for a maximum of five disk expansion drawers per adapter. Refer to Figure 7.

Notes:

• Disk expansion drawers can be cascaded only one level deep.
• The X cable must be routed along the right side of the rack frame.
• The X cable must be attached to the same numbered port on all adapters.

Two SAS adapters to disk expansion drawer - multi-initiator HA JBOD configuration

Figure 29 illustrates connecting two SAS adapters to a disk expansion drawer in a unique JBOD configuration.

Figure 29. Two RAID SAS adapters to a disk expansion drawer in a multi-initiator HA JBOD configuration

Note: This configuration is only supported by the AIX® and Linux® operating systems with specific SAS adapters and requires special user configuration setup. Refer to the SAS RAID controllers for AIX or the SAS RAID controllers for Linux for additional information.

PCIe SAS adapter in PCIe 12x I/O drawer to the internal SAS disk slots

There are several possible configurations for attaching PCIe SAS adapters to the internal SAS disk slots in the PCIe 12X I/O drawer, and multiple ways of setting up the disk layout within the drawer. The disk unit partitions switch setting on the rear of the PCIe 12X I/O drawer controls the grouping of the disk units within the drawer. This will also affect the way the adapter or adapters are cabled to specific ports on the PCIe 12X I/O drawer. The desired switch position should be selected before attaching the AT cables. If the disk unit partitions switch is changed, the PCIe 12X I/O drawer must be powered off and on for the new position to be detected.

All internal disk units are attached using AT cables. There are also options where other external expansion drawers might be connected to these same SAS adapters. External disk expansion drawers are attached using YO cables for single adapter configurations or X cables for two adapter configurations. External media expansion drawers are attached using AE cables for single adapter configurations. External media expansion drawers are not supported for two adapter configurations.

For complete details and examples of these configurations within the PCIe 12X I/O drawer, see Configuring the 5802 disk-drive subsystem. Figure Figure 30 illustrates the rear view of a typical connection from two PCIe SAS adapters to the PCIe 12X I/O drawer. Use the AT cable to attach from an adapter port to a SAS port on the PCIe 12X I/O drawer.

Figure 30. Two RAID SAS adapters to a disk expansion drawer in a multi-initiator HA JBOD configuration