Serial-attached SCSI cable planning

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.

Supported SAS cable information

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

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

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

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

Figure 6. SAS adapter to two disk expansion drawers

Figure 7. SAS adapter to four disk expansion drawers

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.

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

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

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.

Figure 12. SAS adapter to a disk expansion drawer

Figure 13. SAS adapter to two disk expansion drawers

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 and Figure 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.

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

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

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

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

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

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

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

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

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

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