Disk array overview

Disk arrays are groups of disks that work together with a specialized array controller to potentially achieve higher data transfer and input and output (I/O) rates than those provided by single large disks.

The array controller keeps track of how the data is distributed across the disks. RAID 5, 6, and 10 disk arrays also provide data redundancy so that no data is lost if a single disk in the array fails.
Note: This topic and the iprconfig utility use common terminology for disk formats:
  • JBOD

    A Just a Bunch Of Disks (JBOD) disk is formatted to 512 or 4096 bytes per sector. A JBOD disk is assigned a /dev/sdX name and can be used by the Linux® operating system.

  • Advanced function

    An advanced function disk is formatted to 528 or 4224 bytes per sector. This format allows disks to be used in disk arrays. An advanced function disk cannot be used by the Linux operating system directly. The Linux operating system can use an advanced function disk only if it is configured into a disk array.

Disk arrays are accessed in the Linux operating system as standard SCSI disk devices. These devices are automatically created when a disk array is created, and deleted whenever a disk array is deleted. The individual physical disks that comprise disk arrays (or are candidates to be used in disk arrays), which are formatted for advanced function, are hidden from Linux operating system and are accessible only through the iprconfig utility. The Linux operating system sees all JBOD disks. These disks must be formatted for advanced function before they can be used in disk arrays. For information on formatting JBOD disks to make them available for use in disk arrays, see Formatting to JBOD.

An advanced function disk can be configured as:
Array Member
A 528 bytes per sector HDD disk that is configured as a member of an array.
Hot Spare
A 528 bytes per sector HDD disk that can be used by the controller to automatically replace a Failed disk in a Degraded RAID array. A hot-spare disk is useful only if its capacity is greater than or equal to the capacity of the smallest disk in an array that becomes Degraded. For more information about hot-spare disks, see Hot-spare disks.
Array Candidate
A 528 bytes per sector HDD disk that is a candidate for becoming an Array Member or a Hot Spare.
SSD Array Member
A 528 bytes per sector Solid-State disk that is configured as a member of an array.
SSD Hot Spare
A 528 bytes per sector Solid-State disk that can be used by the controller to automatically replace a Failed disk in a Degraded RAID 5, 6, 10, 5T2, 6T2, or 10T2 disk array. A hot-spare disk is useful only if its capacity is greater than or equal to the capacity of the smallest disk in an array that becomes Degraded. For more information about hot-spare disks, see Hot-spare disks.
SSD Array Candidate
A 528 bytes per sector solid-state disk that is a candidate for becoming an Array Member or a Hot Spare.
RI (Mainstream) Array Member
A 528 bytes per sector read intensive (RI) solid-state disk that is configured as a member of an array.
RI (Mainstream) Hot Spare
A 528 bytes per sector read intensive (RI) solid-state disk that can be used by the controller to automatically replace a failed RI/Mainstream disk in a degraded RAID array. A hot-spare disk is useful only if its capacity is greater than or equal to the capacity of the smallest disk in an array that becomes degraded. For more information about hot-spare disks, see Hot-spare disks.
RI (Mainstream) Array Candidate
A 528 bytes per sector read intensive (RI) solid-state disk that is a candidate for becoming an array member or a hot-spare disk in an array.
4K Array Member
A 4224 bytes per sector HDD disk that is configured as a member of an array.
4K Hot Spare
A 4224 bytes per sector HDD disk that can be used by the controller to automatically replace a Failed disk in a Degraded RAID 5, 6, 10, 5T2, 6T2, or 10T2 disk array. A hot-spare disk is useful only if its capacity is greater than or equal to the capacity of the smallest disk in an array that becomes Degraded. For more information about hot-spare disks, see Hot-spare disks.
4K Array Candidate
A 4224 bytes per sector HDD disk that is a candidate for becoming an Array Member or a Hot Spare.
4K SSD Array Member
A 4224 bytes per sector Solid-State disk that is configured as a member of an array.
4K SSD Hot Spare
A 4224 bytes per sector Solid-State disk that can be used by the controller to automatically replace a failed disk in a Degraded RAID 5, 6, 10, 5T2, 6T2, or 10T2 disk array. A hot-spare disk is useful only if its capacity is greater than or equal to the capacity of the smallest disk in an array that becomes Degraded. For more information about hot-spare disks, see Hot-spare disks.
4K SSD Array Candidate
A 4224 bytes per sector Solid-State disk that is a candidate for becoming an Array Member or a Hot Spare.
4K RI (Mainstream) Array Member
A 4224 bytes per sector read intensive (RI) solid-state pdisk that is configured as a member of an array.
4K RI (Mainstream) Hot Spare
A 4224 bytes per sector read intensive (RI) solid-state pdisk that can be used by the controller to automatically replace a failed RI disk in a degraded RAID disk array. A hot-spare disk is useful only if its capacity is greater than or equal to the capacity of the smallest disk in an array that becomes degraded. For more information about hot-spare disks, see Hot-spare disks.
4K RI (Mainstream) Array Candidate
A 4224 bytes per sector read intensive (RI) solid-state pdisk that is a candidate for becoming an array member or a hot-spare disk for in an array.
4K ENL Array Member
A 4224 bytes per sector Enterprise Nearline (ENL) hard disk drive (HDD) pdisk that is configured as a member of an array.
4K ENL Hot Spare
A 4224 bytes per sector ENL HDD pdisk that can be used by the controller to automatically replace a failed ENL disk in a degraded RAID disk array. A hot-spare disk is useful only if the capacity is greater than or equal to the capacity of the smallest disk in an array that becomes degraded. For more information about hot-spare disks, see Hot-spare disks.
4K ENL Array Candidate
A 4224 bytes per sector ENL HDD pdisk that is a candidate for becoming an array member or a Hot Spare disk in an array.
The Display Hardware Status option in the iprconfig utility can be used to display these disks and their associated resource names. For details regarding how to view the disk information, see Viewing device status. The following sample output is displayed when the Display Hardware Status option is invoked:
+--------------------------------------------------------------------------------+
|                             Display Hardware Status                            |
|                                                                                |
|Type option, press Enter.                                                       |
|  1=Display hardware resource information details                               |
|                                                                                |
|OPT Name   PCI/SCSI Location          Description               Status          |
|--- ------ -------------------------- ------------------------- ----------------|
|           0000:00:01.0/0:            PCI-X SAS RAID Adapter    Operational     |
|    sda    0000:00:01.0/0:4:2:0       Physical Disk             Active          |
|    sdb    0000:00:01.0/0:4:5:0       Physical Disk             Active          |
|           0000:00:01.0/0:4:10:0      Enclosure                 Active          |
|           0000:00:01.0/0:6:10:0      Enclosure                 Active          |
|           0000:00:01.0/0:8:0:0       Enclosure                 Active          |
|           0002:00:01.0/1:            PCI-X SAS RAID Adapter    Operational     |
|    sdc    0002:00:01.0/1:0:1:0       Physical Disk             Active          |
|    sdd    0002:00:01.0/1:0:2:0       Physical Disk             Active          |
|           0002:00:01.0/1:0:4:0       Advanced Function Disk    Active          |
|           0002:00:01.0/1:0:5:0       Advanced Function Disk    Active          |
|           0002:00:01.0/1:0:6:0       Advanced Function Disk    Active          |
|           0002:00:01.0/1:0:7:0       Hot Spare                 Active          |
|    sde    0002:00:01.0/1:255:0:0     RAID 0 Disk Array         Active          |
|           0002:00:01.0/1:0:0:0         RAID 0 Array Member     Active          |
|    sdf    0002:00:01.0/1:255:1:0     RAID 6 Disk Array         Active          |
|           0002:00:01.0/1:0:10:0        RAID 6 Array Member     Active          |
|           0002:00:01.0/1:0:11:0        RAID 6 Array Member     Active          |
|           0002:00:01.0/1:0:8:0         RAID 6 Array Member     Active          |
|           0002:00:01.0/1:0:9:0         RAID 6 Array Member     Active          |
|           0002:00:01.0/1:0:24:0      Enclosure                 Active          |
|           0002:00:01.0/1:2:24:0      Enclosure                 Active          |
|                                                                                |
|e=Exit   q=Cancel   r=Refresh   t=Toggle                                        |
+--------------------------------------------------------------------------------+

Disk array, physical disk, and I/O adapter (IOA) states are displayed in the fifth column of the Display Hardware Status screen.