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Adaptec 2420SA User Guide - Page 76

RAID 6 Arrays, a RAID 60 array-also known as dual drive failure

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Appendix B: Understanding RAID ● 76 RAID 6 Arrays A RAID 6 array-also known as dual drive failure protection-is similar to a RAID 5 array because it uses data striping and parity data to provide redundancy. However, RAID 6 arrays include two independent sets of parity data instead of one. Both sets of parity data are striped separately across all disk drives in the array. RAID 6 arrays provide extra protection for your data because they can recover from two simultaneous disk drive failures. However, the extra parity calculation slows performance (compared to RAID 5 arrays). RAID 6 arrays must be built from at least four disk drives. Maximum stripe size depends on the number of disk drives in the array. Disk Drive 1 250 GB Drive Segment Size (Smallest Disk Drive) Disk Drive 2 250 GB Disk Drive 3 400 GB Disk Drive 4 400 GB Disk Drives in Logical Drive Disk Drive 1 1 P1 ... P2 Disk Drive 2 2 P2 ... 449 Disk Drive 3 P1 3 ... P1 Unused Space = 150 GB Disk Drive 4 P2 4 ... 500 Unused Space = 150 GB Based on the drive segment sizes used: RAID 6 Logical Drive = 500 GB plus parity (P1 & P2) RAID 60 Arrays Similar to a RAID 50 array (see page 75), a RAID 60 array-also known as dual drive failure protection-is built from eight disk drives configured as two or more RAID 6 arrays, and stripes stored data and two sets of parity data across all disk drives in both RAID 6 arrays. Note: Because they support four disk drives only, the Adaptec 2420SA RAID controller can't support RAID 60 arrays. Two sets of parity data provide enhanced data protection, and striping improves performance. RAID 60 arrays also provide high data transfer speeds.

Section	Page
About This Guide	11
What You Need to Know Before You Begin	12
Terminology Used in this Guide	12
How to Find More Information	12
Kit Contents and System Requirements	13
Kit Contents	14
System Requirements	14
About Your RAID Controller	15
Standard RAID Controller Features	16
Array-level Features	16
Advanced Data Protection Suite	16
Adding Enhanced Features	17
Using a Feature Key to Unlock Enhanced Features	17
Adding a Battery Backup Module	17
Upgrading the Controller Firmware	17
About the Adaptec 4000	18
About the Adaptec 4800SAS	19
About the Adaptec 4805SAS	20
About the Adaptec 2420SA	21
About the Adaptec 2820SA	22
About the Adaptec 2130SLP	23
About the Adaptec 2230SLP	24
Getting Started	25
Choosing a RAID Level	26
Selecting Disk Drives	27
Disk Drives for SAS Controllers	27
Disk Drives for SATA Controllers	27
Disk Drives for SCSI Controllers	27
Selecting Cables	28
SAS Cables	28
SATA Cables	29
SCSI Cables	29
Installation Options	30
Basic Installation Steps	30
Installing with an Operating System	30
Installing on an Existing Operating System	30
Installing the Controller and Disk Drives	31
Before You Begin	32
Installing the Controller	32
Connecting Disk Drives to SAS RAID Controllers	33
Connecting Directly to the Controller	33
Connecting to a System Backplane	34
Connecting Disk Drives to SATA RAID Controllers	35
Connecting Disk Drives to SCSI RAID Controllers	35
Connecting External Devices	35
Next Steps	36
Monitoring Disk Drives with Adaptec Storage Manager	36
Creating a Bootable Array	37
Setting the Boot Controller	38
Creating an Array	38
Creating an Array with the ACU	38
Creating an Array with Adaptec Storage Manager	40
Making Your Array Bootable	41
Installing the Driver and an Operating System	42
Before You Begin	43
Creating a Driver Disk	43
Installing with Windows	44
Installing with Red Hat Linux	44
Installing with SUSE Linux	45
Installing with NetWare	45
Installing with OpenServer	46
Installing with Solaris	46
Installing with UnixWare	47
Installing with VMWare	47
Installing with FreeBSD	47
Installing the Driver on an Existing Operating System	49
Before You Begin	50
Creating a Driver Disk	50
Installing on Windows	51
Installing on Red Hat or SUSE Linux	51
Installing on NetWare	51
Installing on OpenServer	52
Installing on Solaris	52
Installing on UnixWare	53
Installing on VMWare	53
Installing on FreeBSD	53
Managing Your Storage Space	55
About Adaptec Storage Manager	56
Installing Adaptec Storage Manager	56
About the Adaptec RAID Controller Configuration Utility	56
About the Adaptec RAID Configuration Utility	57
About the Adaptec Flash Utility	57
Which Utility Should I Use?	57
Solving Problems	58
Troubleshooting Checklist	59
Silencing the Alarm	59
Recovering from a Disk Drive Failure	59
Failed Disk Drive Protected by a Hot Spare	60
Failed Disk Drive Not Protected by a Hot Spare	60
Failure in Multiple Arrays Simultaneously	60
Disk Drive Failure in a RAID 0 Array	60
Multiple Failures in the Same Array	61
Resetting the Controller	61
Introduction to Serial Attached SCSI	62
Terminology Used in This Chapter	63
What is SAS?	63
How Do SAS Devices Communicate?	64
What’s a Phy?	64
What’s a SAS Port?	65
What’s a SAS Address?	65
What’s a SAS Connector?	65
What do SAS Cables Look Like?	65
How are Disk Drives Identified in SAS?	66
What are the SAS Connection Options?	66
Direct-attach Connections	66
Backplane Connections	66
SAS Expander Connections	67
How is SAS Different from Parallel SCSI?	68
Understanding RAID	69
Understanding Drive Segments	70
Nonredundant Arrays (RAID 0)	70
RAID 1 Arrays	71
RAID 1 Enhanced Arrays	71
RAID 10 Arrays	72
RAID 5 Arrays	73
RAID 5EE Arrays	74
RAID 50 Arrays	75
RAID 6 Arrays	76
RAID 60 Arrays	76
Selecting the Best RAID Level	77
Using the Adaptec RAID Configuration Utility	78
Introduction to the ARC Utility	79
Running the ARC Utility	79
Navigating the ARC Utility	79
Using the ACU to Create and Manage Arrays	79
Creating a New Array	79
Managing Existing Arrays	80
Creating Bootable Arrays	80
Initializing Disk Drives	80
Rescanning Disk Drives	80
Secure Erasing Disk Drives	81
Stopping a Secure Erase	81
Using the -Select Utility to Modify Controller Settings	81
Opening a -Select Utility	81
Applying Changes and Exiting	81
Modifying Your Controller’s Configuration	82
General Controller Settings	82
SAS-specific Controller Settings	83
SATA-specific Controller Settings	83
SCSI-specific Controller Settings	84
SCSI Device Settings	84
SCSI Channel Interface Settings	84
Formatting and Verifying Disk Drives	85
Viewing the Event Log	85
Using the Array Configuration Utility for DOS	86
Getting Started	87
Working in the ACU Using Menus	87
Running the ACU Using Scripts	88
About Playback Mode	88
About Record Mode	89
Creating the Script File Manually	89
Entering Comments in the Script File	89
Array Definition Block Keywords	90
Array Keyword	90
Drives Keyword	90
End Keyword	91
HotspareDrives Keyword	91
InitializeAll Keyword	91
Method Keyword	92
ReadCache Keyword	92
Size Keyword	92
StripeSize Keyword	92
Type Keyword	93
Wait Keyword	93
WriteCache Keyword	93
Channel Definition Block Keywords-SCSI only	93
Channel Keyword	93
ControllerID Keyword	94
End Keyword	94
ACU Error Codes	94
Sample Scripts	95
Sample Scripts for SCSI and SAS Controllers	95
Sample Script for SATA Controllers	96
Using the Adaptec Flash Utility	97
System Requirements	98
Compatibility Notes	98
Before You Begin	98
Obtaining the Firmware	98
Creating the Firmware Floppy Disks	99
Running the Menu-based AFU	99
Running the AFU from the Command Line	100
AFU Commands	100
List	100
Save	100
Update	101
Verify	102
Version	102
Help	102
Updating the Flash Using the AFU Command Line	103
Safety Information	104
Electrostatic Discharge (ESD)	104
Technical Specifications	105
Environmental Specifications	106
DC Power Requirements	106
Current Requirements	106

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Appendix B: Understanding RAID

●

RAID 6 Arrays

A RAID 6 array—also known as dual drive failure protection—is similar to a RAID 5 array

because it uses data striping and parity data to provide redundancy. However, RAID 6 arrays

include

two

independent sets of parity data instead of one. Both sets of parity data are striped

separately across all disk drives in the array.

RAID 6 arrays provide extra protection for your data because they can recover from two

simultaneous disk drive failures. However, the extra parity calculation slows performance

(compared to RAID 5 arrays).

RAID 6 arrays must be built from at least four disk drives. Maximum stripe size depends on

the number of disk drives in the array.

RAID 60 Arrays

Similar to a RAID 50 array (see

page 75

), a RAID 60 array—also known as dual drive failure

protection—is built from eight disk drives configured as two or more RAID 6 arrays, and

stripes stored data and two sets of parity data across all disk drives in both RAID 6 arrays.

Note:

Because they support four disk drives only, the Adaptec 2420SA RAID controller can’t

support RAID 60 arrays.

Two sets of parity data provide enhanced data protection, and striping improves performance.

RAID 60 arrays also provide high data transfer speeds.

Disk Drive 1

Disk Drive 2

Disk Drive 3

Disk Drive 4

250 GB

400 GB

Drive Segment Size

(Smallest Disk Drive)

Disk Drive 2

Disk Drive 3

Disk Drive 4

Disk Drive 1

P1 ...

P2 ... 449

3 ...

4 ... 500

Unused Space = 150 GB

Disk Drives in Logical Drive

Based on the drive segment sizes used:

RAID 6 Logical Drive = 500 GB plus

parity (P1 & P2)

Unused Space = 150 GB