You can mirror an existing NSS pool partition by using the Create RAID command with the part=<existing_partition_name> option as follows:
nlvm [nlvm_options] create raid name=<raid_name> raid=1 [type=nss|sbd] part=<pool_partition_name> device=<device_name>
This command specifies the existing pool partition as the first segment of a RAID1 mirror. You must specify the device option one time with the device to use as its mirror. You do not specify a size in the command. The size of the existing partition determines the amount of space that is used for the mirrored segment. The partition type created for the mirror is the same type as the original partition. After you mirror the partition, you manage the RAID1 device by using the normal NSS software RAID management tools and commands.
For example, if POOL1 uses partition sdc1.1, the following command creates an NSS software RAID 1 mirrored device named POOL1RAID1. The pool’s existing partition becomes the first segment of the RAID, and its existing data is mirrored to device sdf.
nlvm create raid name=POOL1RAID1 raid=1 part=sdc1.1 device=sdf