Ed. Note: This is a fairly common question that we get. Sizing is always a pain, especially when you're moving into a new setup. So if you have any wisdom on the matter, please post in the comments.
We are a K-12 school (K-8 at one site and 6-12 at the other) that is using a Mac Pro at each site to house home folders as well as run OD
My first question is this: Should one server be handling both of these tasks? If not, is there a economical way to change this. I ask because when a class atempts to logon, there is a serious bottle-neck! To eliminate this at one site, I made the older students (that have larger home folders) mobile with assigned seating in the lab of iMacs. This seems to have solved the speed issue and I'd like to try something similar at the other site which has a laptop cart of macbooks as its lab.
So here's the second question: How many accounts can live on a single workstation and work well?
Any help you could offer would be great!
Server & Clients 10.5.6
by 
Hi, my environment is a K-8 with 7 elementary schools k-5 and 2 middle schools 6-8. Currently we use three Xserves at the elementary level. One of them runs OD, DHCP, netboot etc.. another for student home folders, the last for teacher home folders. I wouldn’t necessarily say that you will see a dramatic increase in speed if you separate your ODM from your home stores but that will largely depend on how many users you have accessing these share points. Mobile accounts will allow for the most increased log in speeds and I would recommend using them everywhere you can.
All of our machines use mobile accounts. In the mobility settings you can set account expiry. For example, if you have a class of students in the lab for a specific project for x amount of weeks, you can set their accounts to expire after a given amount of time without logging back into those accounts; thus controlling the amount of accounts and storage utilization on the local machine. I have machines with 50+ accounts on them (though this is rare) and they continue to perform as expected. Also, mobile accounts provide the benefit of ignoring items to sync. On all of my machines, teacher and student, I ignore all iLife projects, music, movies etc.. from being synced as this dramatically decreases log in times as you don’t have 10gb home folders moving across the network and gives me a much larger amount of free space on my servers. You may have political battles enforcing mobile accounts as teachers don’t seem too happy with needing to control which machine a student sits at or which MacBook they get from a cart. This was a large issue for us initially, but when they see the speed benefits they tend to side with you.
Also, a good way to help the younger students remember which machine their mobile account resides on is to manage the login window preferences to show mobile users and local users. This way it will show a list of the mobile accounts that live on the machine, so when they look at an iMac they will quickly be able to evaluate if they should sit there.
Hope this helps.
—
Matt
First question: One machine should be able to handle this fine, with some considerations —
The initial bottle neck for speed would be networking if you are using a single NIC to attach the server to the network.
Are the servers on the same switches as the workstations? Is there suitable free bandwidth between switches if this is not the case?
Teamed/Bonded NICs from the MacPros may see a large increase in speed. The bottle neck then becomes harddrive speed. Ideally you’d have a RAID card for these MacPros which would see some increase in speed, though adding this means the machines start to approach the cost of an Xserve.
Ensuring several folders for the Network home folders are mapped to a local area of each machine significantly reduces load on the server. Items to investigate remapping here are Cache folders and even Desktop folders (depending on how the machines are used, some places have stipulated to users that the desktop folder is a temporary working space only, to good effect)
Also ennsuring other temp files from other programs go to local drives.
Another option would be to investigate External home accounts that students (media or video students perhaps) with very large amounts of data can carry around on an external drive.
You second question is a bit ambiguous. You could have many, many users. It depends on what each user is likely to use on each machine and therefore how large there home folders will be. On current machines even with 10users per machine that still gives them about 20gig each to play with.
Another option to consider here is to ensure home folders are stored on a volume other than the boot partition (easy with Leopard server and clients, see managed preferences to specify the path for new mobile homes). Just split the drives on your machines into system (say 30-40GB) and the rest for storage and scratch.
Hope this helps, even a little.
I talked to a few of my friends who have a masters degree in management and we agreed on the fact that your school doesn’t need two servers, but I have to point out a matter that might help you cut your costs. I have no idea why you chose a Mac server when there are other cheaper options which will work as fine as the one you have now. Hope you find my advice useful.