Just in case anyone was curious, the consensus was that it should have little or no impact to add a disk to a volume, and that is the way it actually turned out. Physically adding the drive to the shelf froze it for 10-15 seconds, prompting my initial concern and question. The 'vol add vol0 1' command took upwards of 5 minutes to zero the disk, but the actual increase in volume size was instantaneous after the zeroing completed. There was no noticeable increase in CPU or NFS ops during the zeroing or addition (although our traffic is rather bursty in nature, but I did not see any sudden big numbers in CPU or ops).
-- Frank Smith fsmith@hoovers.com Systems Administrator Voice: 512-374-4673 Hoover's Online Fax: 512-374-4501