So, my apologies.. Sam corrected me. This changed with the new blockmap structure in ONTAP 6.0 and above (all my testing was with 5.3.7R3). I do not need "reprogramming" - I don't live in California. :)

I was not saying create a new volume. I was saying create a new RAID group in the existing volume. This is where the 'raidsize' volume option comes in. You can do it manually, of course, but 'raidsize' is set for each volume (not the whole filer), and it's less error-prone to change 'raidsize' to the desired value.

You can mix drive sizes within volumes without any problem, but all the drives in a given RAID group in the volume should be the same size.

Set 'raidsize' on the volume in question to the size of the existing 18GB drive RAID group, run 'sysconfig -r' for details. When you go to add the 36GB drives - you will have to add at least two if the RAID group is already at 'raidsize' - it will automatically create a new RAID group with your spiffy new 36GB drives. You will lose one drive to parity, but it could avoid performance woes down the road.

Lacking ASCII artistic skills, imagine having ten small juice glasses and two big ice tea glasses all lined up in a row. This is where your water (essential for all life, also known as "data") goes. As you fill up the small juice glasses, you can only keep pouring into the two big ice tea glasses, but you won't be able to pour it nearly as fast as you could if you were filling up more glasses.

It is still a bad idea to mix drive sizes within a RAID group, because of what can happen to performance as things start to fill up. Creating a new RAID group is still (in my opinion), the way to go, but of course it's your data, your way. If capacity is more important than performance, you don't want to use a precious 36GB drive for parity.

- Justin

-----Original Message----- From: Jeff Bryer [mailto:bryer@sfu.ca] Sent: Wednesday, April 25, 2001 9:48 PM To: Justin.Sullivan@netapp.com Cc: toasters@mathworks.com Subject: Re: Adding a 36gb shelf to F740 with 18gb shelves

Thanks Justin. So we can't change the parity disk from an 18gb disk to a 36gb disk kind of on the fly. We'd have to create a new volume and do a vol copy or some such thing. Not sure where we got the idea we could 'upgrade the parity disk'.

So we either have to buy 18gb shelves or re-architect our layout. (or waste half a disk adding a 36gb to an 18gb set but that's not a great option as our volume is growing quickly).

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.

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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