I'm going to set up a ZFS mirror using two 1TB disks for an offsite backup for when I head off to school this fall... and I'm trying to plan ahead.

My question is:

Once those disks are full/nearing end of life/making grinding noises, how do I migrate the zpool off of one set of physical disks and onto another while growing the zpool to fill any additional space in the new disks?

I guess I could just make a new zpool on the new disks and copy everything over using "cp -a /oldbackup /newbackup", but that has to have some drawback, right?

Thanks.