ADD UNIT is used to create UNITs (logical storage units
comprising of 1 or more hard drives).
Format:
ADD UNIT <unit_n> / <qualifiers>
1 – Parameters
Unit_n (the unit number can range from 0-31)
2 – Qualifiers
2.1 /ADG
Specifies the RAID type for the UNIT as Advanced Data Guard (ADG).
2.2 /CACHE
Determines whether the controller's cache should be used for the
UNIT. Caching is ON by default. To disable caching, use a /NOCACHE
qualifier with SET UNIT or ADD UNIT commands.
2.3 /DISK
Specifies the disk numbers to be used to form the UNIT. Multiple
disks must be enclosed in parenthesis.
Format:
/DISK=(disk numbers[,...])
Note: The disk numbers for the existing disks can be obtained
using the SHOW DISKS command.
2.4 /IDENTIFIER
This is the user-defined identifier for the unit. This identifier
is used by OpenVMS to name the device. The value of the identifier
can be between 1- 9999
Note: Identifier is not required for Smart Array Controllers.
Format:
/IDENT= n
2.5 /JBOD
Specifies the RAID type to be JBOD. This is also synonymous to
RAID 0.
2.6 /PARTITION
Specifies the partition number to be used for a given UNIT. The
first unit that is created on a disk/disk group will automatically
be assigned the partition number 0. The units that are subsequently
created on this disk/disk group will need to be created with partition
numbers in a sequential order.
Format:
/PART=(partition_number)
2.7 /RAID_LEVEL
Specifies the RAID type of the UNIT. The support values for this
qualifier are 0, 1, 5, 50, and 60.
- RAID 0 is Data Striping
- RAID 1 is Disk Mirroring
- RAID 5 is Data Striping with Striped Parity
- RAID 50 is Data Striping across RAID 5 arrays
- RAID 60 is Data Striping across RAID 6 arrays
Format:
/RAID=[(0 | 1 | 5 | 50 | 60)]
Note:
- When minimum four disks are supplied to create a RAID 1 unit,
the controller creates a RAID 10 unit; which is Data Striping
across RAID 1 arrays.
- SHOW UNITS displays "Logical Volume Raid Level: RAID 1" for the
RAID 10 units. If the data disks used by logical unit number (LUN)
are more than two disks, the implementation of that LUN is
RAID 10.
2.8 /SIZE
Specifies the size of the UNIT. When the size qualifier is
not specified, the size defaults to the Maximum capacity of
the disks depending on the RAID level.
Format:
/SIZE=#(Gb | Mb | Kb | %)
2.9 /SPARES
Specifies the disk numbers to be used as spare disk(s). Multiple
disks must be enclosed in parenthesis. Assigning a spare disk to
an unit in a drive group will assign the spare disk to all the
configured units in the drive group.
If an unit is created on a disk group to which a spare disk is
assigned, then the spare disk will be configured to the new unit
(if it is not a RAID 0 unit). One spare disk can be assigned to
multiple drive groups.
Ensure that the size of the spare disk is at least equal to the
size of the smallest drive in the drive group.
Format:
/SPARE=(disk_number[,...])
Note: The disk numbers for the existing disks can be obtained
using the SHOW DISKS command.
2.10 /STRIPE_SIZE
Specifies the stripe size for a given RAID volume. Stripe size
must be one of 8, 16, 32, 64, 128, and 256 values. Raid 5 and ADG
are limited to a maximum 64 KB stripes. RAID 0 and 1 default to 128
KB stripes, and RAID 5 and ADG default to 16 KB stripes.
SAS Smart Array Controllers with Firmware 5.0 onwards support
512 KB stripe size with RAID5.
Format:
/STRIPE=(stripe_size)
2.11 /VERBOSE
Provides logging that can be interpreted by engineering.
3 – Examples
- ADD UNIT 3/ID=1003/DISK=103/JBOD/PARTITION=0/SIZE=8GB
- ADD UNIT 4/ID=1004/DISK=103/JBOD/PARTITION=1/SIZE=10GB
- ADD UNIT 5/ID=1005/DISK=103/JBOD/PARTITION=2/SIZE=8GB
In the above-mentioned examples, 3 units are being created on disk
103. Notice that the partition numbers are provided in sequential
order on the same disk/disk group.
Consider the following command sequence:
- ADD UNIT 3/ID=1003/DISK=103/JBOD/PARTITION=0/SIZE=8GB
- ADD UNIT 4/ID=1004/DISK=103/JBOD/PARTITION=2/SIZE=10GB
Assuming that there is no unit with partition number '1' on this
disk, the creation of unit 4 will fail since the unit is assigned
the partition number '2' and the assignment is not in sequential
order.
4 – Restrictions
Any two or a combination of all the following qualifiers
cannot be used in conjunction with each other:
/RAID_LEVEL, /JBOD, /ADG