Data Ontap Can Silently Select Varying Disk Sizes Or Array Lun Sizes When Creating An Aggregate; Adding Disks When Varying Sized Disks Are In Use - IBM N Series Manual

the software disk ownership information will be incorrect for the earlier
version and might prevent Data ONTAP from identifying or correctly
assigning the disk.
The disk identification issues cannot be solved except by returning the disk to
the original storage system and removing the software disk ownership
information using the more recent version of Data ONTAP.
To avoid causing disk identification issues, always use the recommended
procedure for removing a data disk, which includes removing the software
disk ownership information from the disk before removing it.
For more information, see the Data ONTAP 8.0 7-Mode Storage Management
Guide.
Note: Gateway systems support disks starting with Data ONTAP 7.3.
Therefore, you cannot move a disk from a gateway system to a gateway
system running a version of Data ONTAP earlier than 7.3.
Data ONTAP can silently select varying disk sizes or array LUN sizes
when creating an aggregate
If disks or array LUNs of varying size are present in your storage system,
relying on automatic disk selection can result in unexpected sizes being
selected by Data ONTAP.
When you create a new aggregate using automatic disk or array LUN
selection, Data ONTAP selects disks or array LUNs based on various criteria
including size, speed, and checksum type. To ensure that the disks or array
LUNs selected are the size you want, specify the disk or array LUN size when
creating an aggregate.
For more information, see the na_aggr(1) man page.

Adding disks when varying sized disks are in use

When you have disks of different sizes available, always specify the disk size
when creating or adding to an aggregate.
To specify the disk size when you add a disk to an aggregate, enter the
following command:
aggr add aggr_name num_disks@size
Example
For example, to add four 635-GB disks to aggr1, enter the following
command:
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IBM System Storage N series: Data ONTAP 8.0.4 7-Mode Release Notes