Appendix D. RAID-3 and Fast RAID-3
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Appendix D. RAID-3 and Fast RAID-3

This appendix explains

Firmware Revision Level-Dependent Differences for RAID-3 Capabilities and Requirements

If the SPs in your Challenge RAID storage system have firmware revision 9.0 and higher (SP model 7305) and RAID agent 1.55 and higher, they are capable of “fast” RAID-3, with enhanced performance. Firmware revision 9.0 and higher divides SP memory into RAID-3 space in addition to storage-system buffer space, write cache space, and read cache space.

Fast RAID-3 has specific SP memory requirements: you must allocate memory specifically for it, and then divide this memory among the RAID-3 LUNs when you bind them.

Table D-1 summarizes differences in how RAID-3 LUNs are bound for SPs of different firmware levels.

Table D-1. RAID-3 Differences Depending on Firmware Revision Level

Type

Firmware Revision

Binding

RAID-3 Memory

Write Caching

Read Caching

RAID-3

8.99 and lower

You must bind exactly five disk modules, selected in any order. If possible, use modules on separate SCSI buses for highest availability (for example, A2, B2, C2, D2, E2).

N/A

Highly recommended

Recommended

Fast RAID-3

9.0 and higher

Before binding, you must allocate RAID-3 memory for the SP, then allocate memory for the LUN. For example, if you allocate 12 MB for an SP, you can assign 6 MB to each of two LUNs owned by that SP, or 4 MB to each of three LUNs owned by that SP.

In a failover system (dual-SP), the SPs must have RAID-3 memory allocated the same way, and each SP must have twice as much RAID-3 memory as each one actually uses in a normally functioning system. For example, if each SP has two LUNs with 3 MB each, the RAID-3 memory for each SP must be 12 MB, so that each SP is able to take over the function of the other SP if it fails. That is, each SP must have enough RAID-3 memory for its own LUNs (2 × 3 MB) plus the other SP's LUNS (2 × 3 MB).

You bind exactly five disk modules, in any order; for highest availability, use modules on separate SCSI buses.

Required

N/A

N/A

Chapter 4 provides detailed information on memory requirements for fast RAID-3 and how to set them.

Determining Firmware Revision Level and RAID-3 Type

To use the command-line interface to see the revision number of an SP's firmware and RAID agent only, use raidcli -d <device> getsp. For systems containing many Challenge RAID chassis assemblies, this parameter is especially useful as an alternative to raidcli getagent.

The syntax is

raidcli -d device getsp

Example output:

Revision 8.20.0, Model: 7624

In the output, Model 7624 is the AMD-based SP (Sauna) and Model 7305 is the PowerPC-based SP (Phoenix).

To use RAID5GUI to determine firmware level and RAID-3 type, use the View Settings window. Select “View Settings” in the Options menu of either the Summary View or Equipment View. This window shows the firmware revision level and the PROM revision (RAID agent) number.

The following figures show the difference:

  • Figure D-1 shows an SP with firmware above 9.0. Note that settings relating to caching are grayed out. The LUN's RAID3 Memory Size entry (lowest line at right) shows a number other than 0, indicating that this system has fast RAID-3.

  • Figure D-2 shows an SP with firmware below 8.9. Note that there is no entry for the LUN's RAID3 Memory Size.

    Figure D-1. Example View Settings Window for RAID-3 in Firmware Revision Level 9.0 and Higher


    Figure D-2. Example View Settings Window for RAID-3 in Firmware Revision Level 8.9 and Lower


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Appendix C. Storage-Control Processor Event-Log Error Codes  Appendix E. Compliance Statements