Cisco UCS C420 Server Installation and Service Guide
RAID Controller Considerations
Downloads: This chapterpdf (PDF - 1.7MB) The complete bookPDF (PDF - 12.43MB) | Feedback

Table of Contents

RAID Controller Considerations

Supported RAID Controllers and Required Cables

Supercap Power Modules (RAID Backup Units)

Mixing Drive Types in RAID Groups

RAID Controller Cabling

Example 1—One Nonexpander and One RAID Controller with Eight Drives

Example 2—Two Nonexpanders and Two RAID Controllers with 16 Drives

Example 3—Two Expanders and One RAID Controller with Sixteen Drives

Restoring RAID Configuration After Replacing a RAID Controller

For More Information

Supported RAID Controllers and Required Cables

This server supports the RAID controller options and cable requirements shown in Table C-1 .


Note Do not mix controller types in the server.


 

Table C-1 Cisco UCS C420 Server Supported RAID Options

Controller
Style
Maximum Drives
Optional SCPM?
RAID Levels
Required Cables1
LSI MegaRAID

SAS 9271CV-8i

PCIe

8 internal2

or 16 internal with expander3

Yes

0, 1, 5, 6, 10, 50, 60

  • One controller with one nonexpander:

1 UCSC-CABLE-S + 1 UCSC-CABLE-L

  • Two controllers with two nonexpanders:

2 UCSC-CABLE-S + 2 UCSC-CABLE-L

  • One controller with two expanders:

2 UCSC-CABLE-S

LSI MegaRAID

SAS 9286CV-8e

PCIe

128 external

Yes

0, 1, 5, 6, 10, 50, 60

Cisco does not sell the cables for external drives.

1.The number and type of cables vary, depending on which type of transition card is used and how many controllers are used. See also RAID Controller Cabling.

2.When using the nonexpander-style transition card, each controller can support 8 drives; you can install two controllers and two nonexpander transition cards to control a total of 16 drives.

3.When using two expander-style transition cards, one controller can control 16 drives.

Supercap Power Modules (RAID Backup Units)

This server supports installation of two supercap power module (SCPM) backup units. The units mount to trays on the removable air baffle (see Replacing the Supercap Power Module (RAID Backup Unit)).

The SCPM is available only when using the LSI MegaRAID-CV controller cards. This module provides approximately 3 years of backup for the disk write-back cache DRAM in the case of sudden power loss by offloading the cache to the NAND flash.

Mixing Drive Types in RAID Groups

Table C-2 lists the technical capabilities for mixing hard disk drive (HDD) and solid state drive (SSD) types in a RAID group. However, see the best practices recommendations that follow for the best performance.

 

Table C-2 Drive Type Mixing in RAID Groups

Mix of Drive Types
in RAID Group
Allowed?

SAS HDD + SATA HDD

Yes

SAS SSD + SATA SSD

Yes

HDD + SSD

No

Best Practices For Mixing Drive Types in RAID Groups

For the best performance, follow these guidelines:

  • Use either all SAS or all SATA drives in a RAID group.
  • Use the same capacity for each drive in the RAID group.
  • Never mix HDDs and SSDs in the same RAID group.

RAID Controller Cabling

The maximum two supported RAID controller cards should be populated in PCIe slots in the following order (see Figure 3-23):

1. PCIe slot 3

2. PCIe slot 5

Refer to the following examples for cable routing guidelines:

For more information about transition cards, see Replacing a Modular Drive Bay Assembly.

Example 1—One Nonexpander and One RAID Controller with Eight Drives

Figure C-1 shows an example of a server that is using one RAID controller in PCIe slot 3 and a nonexpander transition card to control eight drives in the modular drive bay.

Two RAID cables are required (1 UCSC-CABLE-S and 1 UCSC-CABLE-L).

  • The blue line is a 0.8m cable (UCSC-CABLE-S) from the RAID controller SAS 0 connector to the nonexpander connector for PORT 1–4.
  • The red line is a 1m cable (UCSC-CABLE-L) from the RAID controller SAS 1 connector to the nonexpander connector for PORT 5–8.
  • The green line is the cable from the RAID controller to the SCPM backup unit.

Figure C-1 RAID Controller Cabling Guidelines, Nonexpander Transition Card

 

1

Nonexpander transition card

(shown with fan tray removed)

3

RAID controller card in PCIe slot 3

2

SCPM backup unit

(mounted to tray on air baffle)

Example 2—Two Nonexpanders and Two RAID Controllers with 16 Drives

Figure C-2 shows an example of a server that is using two RAID controllers in PCIe slots 3 and 5 and two nonexpander transition cards to control eight drives in each of the two modular drive bays.

Four RAID cables are required (2 x UCSC-CABLE-L and 2 x UCSC-CABLE-S).

  • The upper blue line is a 0.8m cable (UCSC-CABLE-S) from the slot 5 RAID controller SAS 0 connector to the nonexpander connector for PORT 1–4.
  • The upper red line is a 1m cable (UCSC-CABLE-L) from the slot 5 RAID controller SAS 1 connector to the nonexpander connector for PORT 5–8.
  • The violet line is a 1m cable (UCSC-CABLE-L) from the slot 3 RAID controller SAS 0 connector to the nonexpander connector for PORT 1–4.
  • The lower blue line is a 0.8m cable (UCSC-CABLE-S) from the slot 3 RAID controller SAS 1 connector to the nonexpander connector for PORT 5–8.
  • The green lines are the cables from the two RAID controllers to their respective SCPM backup units.

Figure C-2 RAID Controller Cabling Guidelines, Two Nonexpanders and Two Controllers

 

1

Transition cards, nonexpander version

(shown with fan tray removed)

3

RAID controller cards in PCIe slots 3 and 5

2

SCPM backup units
(two, mounted to trays on air baffle)

Example 3—Two Expanders and One RAID Controller with Sixteen Drives

Figure C-3 shows an example of a server that is using one RAID controller in PCIe slot 3 and two expander transition cards to control eight drives in each of the two modular drive bays.

Two RAID cables are required (2 x UCSC-CABLE-S).

  • The upper blue line is a 0.8m cable (UCSC-CABLE-S) from the RAID controller SAS 0 connector to the first expander connector A (for drives 1 through 8).
  • The lower blue line is a 0.8m cable (UCSC-CABLE-S) from the RAID controller SAS 1 connector to the second expander connector B (for drives 9 through 16).
  • The green line is a cable from the RAID controller to the battery backup unit.

Figure C-3 RAID Controller Cabling Guidelines, Two Expanders and One Controller

 

1

Expander transition cards

(shown with fan tray removed)

3

RAID controller card in PCIe slot 3

2

SCPM backup unit

(mounted to tray on air baffle)

Restoring RAID Configuration After Replacing a RAID Controller

When you replace a RAID controller, the RAID configuration that is stored in the controller is lost.

To restore your RAID configuration to your new RAID controller, follow these steps.


Step 1 Replace your RAID controller. See Replacing a PCIe Card in a Motherboard Slot.

Step 2 If this was a full chassis swap, replace all drives into the drive bays, in the same order that they were installed in the old chassis.

Step 3 Reboot the server and watch for the prompt to press F.


Note For newer RAID controllers, you are not prompted to press F. Instead, the RAID configuration is imported automatically. In this case, skip to Step 6.


Step 4 Press F when you see the following onscreen prompt:

Foreign configuration(s) found on adapter.
Press any key to continue or ‘C’ load the configuration utility,
or ‘F’ to import foreign configuration(s) and continue.
 

Step 5 Press any key (other than C) to continue when you see the following onscreen prompt:

All of the disks from your previous configuration are gone. If this is
an unexpected message, then please power of your system and check your cables
to ensure all disks are present.
Press any key to continue, or ‘C’ to load the configuration utility.
 

Step 6 Watch the subsequent screens for confirmation that your RAID configuration was imported correctly:

  • If you see the following message, your configuration was successfully imported. The LSI virtual drive is also listed among the storage devices.
N Virtual Drive(s) found on host adapter.
 
  • If you see the following message, your configuration was not imported. This problem can occur if you do not press F quickly enough when prompted. In this case, reboot the server and try the import operation again when you are prompted to press F.
0 Virtual Drive(s) found on host adapter.
 


 

For More Information

The LSI utilities have help documentation for more information about using the utilities.

For basic information about RAID and for using the utilities for the RAID controller cards, see the
Cisco UCS Servers RAID Guide .

Full LSI documentation is also available:

LSI MegaRAID SAS Software User’s Guide (for LSI MegaRAID)

http://www.lsi.com/DistributionSystem/AssetDocument/80-00156-01_RevH_SAS_SW_UG.pdf