Content database IO utilization depends upon how the system is used. Generally, read access is more of a prominent need, but if your plans include lots of updates and additions of documents or list items then write IO will be important to your decision. Furthermore, different components of SharePoint will have different needs such as the tempdb and Search db. So to really answer the question you need to ask how will my company be using MOSS. The search and temp databases are high IO resources as you stated and explained in the in greater detail in the documentation below.
I would recommend the following resources
Database Administration Tasks
Estimating SharePoint Performance
Estimate performance and capacity requirements (Office SharePoint Server)
The most important DBA doc which just became available in Dec though is White paper: Performance recommendations for storage planning and monitoring. I have attached that file as well as the link. So what this really means to you is that to effectively plan your DB environment for performance and scalability, you first need the business to provide you with at a minimum what they plan on doing.
· Planning and architecture for Office SharePoint Server 2007 (http://go.microsoft.com/fwlink/?LinkID=105576&clcid=0x409)
· Planning and architecture for Windows SharePoint Services 3.0 technology (http://go.microsoft.com/fwlink/?LinkID=105577&clcid=0x409)
All this will lead you to Windows SharePoint Services collaboration environments and eventually this Physical Database Storage Design or Estimate performance and capacity requirements for Windows SharePoint Services collaboration environments (Office SharePoint Server) and eventually to Physical Database Storage Design depending upon the farm being MOSS or WSS.
This will then eventually lead you to Predeployment I/O Best Practices.
So what this all boils down to is the business has to tell you as the DBA what they are going to do and how they plan to use MOSS. To answer your other questions about planning for the tempdb see below from the attached White paper: Performance recommendations for storage planning and monitoring.
Ideally, the tempdb, content databases and SQL Server transaction logs should all be on separate physical hard disks.
· When prioritizing data among faster disks, use the following ranking:
1. tempdb data and transaction logs
2. Database transaction log files.
3. Search database.
4. Database data files.
Note: In a heavily read-oriented portal, prioritize data over logs.
· Testing and customer data have shown that Office SharePoint Server farm performance can be significantly impeded by insufficient disk I/O for the tempdb. To avoid this issue, allocate dedicated disks for the tempdb file. If a high workload is projected or monitored (Avg. Disk Sec/Read or Avg. Disk Sec/Write is greater than 20 ms), you may need to ease the bottleneck by either separating the files across disks, or replacing your disks with faster disks.
· For best performance, place the tempdb file on a RAID 10 array. The number of data files should be equal to the number of core CPUs, and of equal size.
· Separate database data and transaction log file across different disks. If files must share disks because the files are too small to warrant a whole disk or stripe or you have a shortage of disk space, put files on the same disk that have different usage patterns, so that simultaneous access requests will be unlikely.
· Consult your storage hardware vendor for how to configure all logs and the Search databases for write optimization for your particular storage solution.
· Pre-size your data and log files.
· Do not rely on AUTOGROW, instead manage the growth of data and log files manually. You may leave AUTOGROW ON for safety reasons, but you should proactively manage the growth of the data files.
· Allocate dedicated spindles for the Search database.
Depending upon the specific hardware and configuration, you are going to see different results. The WP and articles we publish usually display specific hardware examples. IO of course is going to be the your biggest focus, so I would strongly encourage you to engage your hardware provider as in many cases they will have specific recommendations for each component.
Creating Effective Enterprise Portals by Using SharePoint Server 2007
MSIT - Deploying and Supporting Enterprise Search
Microsoft Office SharePoint Server 2007 on HP ProLiant Servers - Performance Summary
Microsoft Office SharePoint Server 2007 Sizing and Configuration Tool
How Dell Does IT - SharePoint Portal Server 2007
Dell MOSS Portal
Dell MOSS Sizing Guide