Yes, you're going to have a problem.. :(
If you add 36GB drives to an existing RAID group of 18GB disks, the 36GB disks will be reported and used as 18GB drives.
Once a RAID group is established with a parity drive of xxGB, any disks added to that RAID group will only be used to the same capacity (xxGB) as the parity drive.
If you reverse the situation, and add 18GB drives to an existing 36GB drive RAID group, all drives will be used to their full capacity, but you will run into performance troubles as the volume fills up and the system is forced to write only to the larger disks, thereby reducing the number of physical spindles working for you.
You will definitely want to create a new RAID group (or a new volume) for your 36GB drives to take advantage of the higher capacity.
--- Justin Sullivan Network Appliance, Technical Support Engineer Network Appliance Certified Associate justins@netapp.com Get answers NOW! - NetApp On the Web - http://now.netapp.com Tech Support Hotline: 1-888-4NETAPP
-----Original Message----- From: Jeff Bryer [mailto:bryer@sfu.ca] Sent: Wednesday, April 25, 2001 6:26 PM To: toasters@mathworks.com Subject: Adding a 36gb shelf to F740 with 18gb shelves
We have an F740 with 3 shelves of 18GB disks. It's config'd as two volumes (two raid sets). We've almost outgrown the capacity (we're down to one hot spare and a free disk).
We want to add a new disk shelf to the system, but we're wondering if we're going to lose anything by going to a shelf of 36gb disks. We don't have any intention of adding new volumes (or new raid sets), just growing the existing volumes.
Can we add a shelf of 36gb disks and then switch our 2 existing 18gb parity disks over to 36gb disks? We'd keep a 36gb disk as a hot spare and use all of the 18gb disks in the volumes (including the 2 freed up parity disks and the freed up hot spare). Are we going to run into problems with this? Or do we need to keep an 18gb disk around as a hot spare as well (ie when an 18gb disks dies and uses a 36gb disks as a hot spare, can we force it to go back to the 18gb disk once the faulty 18gb disk has been replaced?).
Are the 36gb disks going to be used at full capacity in this situation (when mixed with the 18gb)? Or is there a better way to do this?
Thanks,