This used to be the case. Back in the sad days of bug 13880.
http://now.netapp.com/NOW/cgi-bin/bol?Type=Detail&Display=13880
This issue is resolved with the whiz-bang spacemap as implemented in 6.0
and later, where we have a much better idea of where all the space is,
and won't paint ourselves into a corner if we don't have to.
As to the parity disk question, to quote our own dogfood:
http://now.netapp.com/NOW/knowledge/docs/ontap/rel601r3/html/sag/disks4.htm
"Parity disk determination:
If an added disk is larger than the existing parity disk, the added disk
becomes the parity disk, and the former parity disk becomes a data
disk."
We'll bring Justin back to the lab for reprogramming.
Now, a reasonable follow up question would be: can I make a new raid
group out of all 36G drives, and not waste any 36G drives as parity
disks on 18G raid groups? My understanding is that, if you change the
volume's raid group size to whatever the size of the 'last' 18G disk
raid group is, we'll make a new raid group out of the 36G drives. I'm
going to test this now.
--
Sam Rafter Escalations Jerk
Network Appliance rafter@netapp.com
"Sullivan, Justin" wrote:
>
> 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,
>
> --
> Jeff Bryer bryer@sfu.ca
> Systems Administrator (604) 291-4935
> Academic Computing, Simon Fraser University
