Same or Separate Installation of Altiris

In our environment we basically have 3 different servers for DS, NS, and the SQL in a VM environment. I think it's a good practice to have them separate. For whatever reason, if you have them all on the same server and it crashes, then you're in a REALLY bad place. Also, you'll notice an improvement in the performance due to the fact that the load on the server will be cut by 2/3 in case you put all 3 on different servers.

We don't have HelpDesk, but we do have our DS (virtual), NS and SQL on different servers. I think the performance is better that way. But, it really depends on how many clients you have.

I agree, one of the main consideration about separate or maintain in the same server is calculate how many clients do you have to manage.
For my side I have in one VM server and works well (about 500 clients).

We have around 600 clients.

From my expirence, if you choose to run SQL off box, make sure you go with SQL Server 2005. We started our off box expirence here running SQL Server 2000 and noticed a significant reduction in speed, expecially running the DS console. Where it would virutally no time to open, it would take up to 2 minutes. Once we upgraded to SQL 2005, it was like it was all on the same box again.

With only 600 clients, you could probably get away with all on the same box. Just make sure you have a good backup procedure if you do go all on the same box. As mabdelnabi said, it crashes you could be hurting.

Since we're speaking SQL2005. we had to switch to SQL authentication instead of Application -Like Windows authentication through Active Directory.- We were running into time outs and the NS kept loosing connection to the SQL Server. All problems were gone once we switched to SQL authentication. That could be due to the fact that our AD is running on Server2000, NS on Server2003, and we're running SQL2005 for thr DB. The moral advice is to switch to SQL Authentication if you're looking into separating them to avoid some headaches
in the future.