Its not that old... I have 3 D270...
Im in search also for I have 4GB drives... or no drives at all... Anyway I cant use them because my wife complains of the noise so they are in a garage for now...
I would not advise you to go for 11iv3 but the monkey in me in tempted to say try anyway and give us some feed back...
About the disks I dont know if you can put 36GB disks in them for you would have to say about the boxes themselves: Are they with the hot swap option: When you open the front door you see empty slots. if they are you can only put 2 disks in them (D2XX but can plug behind on the card to an external cab...) you should have up to 5...
If you find two 18 GB you are well off I suppose at the condition you want to install something minimalist to play with but still have all HP-UX installed... and be able to activate the mirror, if you dont have mirror-ux then you have enough to install I suppose one oracle instance...
My concern is memory : 256MB is little even for running HPUX11.00 (runs fine on these boxes...) You would need 1GB to make a 11.11 work decently and I cant remember quite but you are limited on what you can add... not sure for D380 though (for a D220-230 I think its 2GB and even that I am not sure anymore (was a few years ago since I last updated one... but remebred there were restrictions) I suppose there were also some firmware updates to do...
If you wish to go 64bit OS and accept it will be slower, this is what I would do ( since its the thing I wanted to but never could...) Install a 11iv1 (11.11) and upgrade to 11.23 and see what it represents in terms of time to get the lot working perfectly... then make a recovery tape.
Since its works, then install from scratch in 11.23 and compare results...
Now up to you to try 11.31 but I am not sure the firmware is compatible, you would have to check first...
Does your unit have a DAT ?
You may already had a look at:
http://h20000.www2.hp.com/bizsupport...ctID=c00323308
P.S the latest firmware is 42.11...