I don't expect a straightforward silver bullet answer to this, but what are the best practices for ensuring good performance for SharePoint 2007 sites?
We've a few sites for our intranet, and it generally is thought to run slow. There's plenty of memory and processor power in the servers, but the pages just don't 'snap' like you'd expect from a web site running on powerful servers.
We've done what we can to tweak setup, but is there anything we could be missing?
Just a few ideas...
Is displaying your pages as slow when doing it from the Server or from a Client? If slower from client, do check your network.
Are your pages very "heavy"? (means, many elements, web parts and so on?) Than maybe it's normal.
Have you noticed they load slowlier since you've add one specific web part? Maybe there's some issues with that specific web part (for example, it's accessing to a document library that has many -thousands of- documents). If that's the case, try to deactivate that specific web part and see if the performance works better.
I noticed that Sharepoint loves to add a ton of JavaScript. If you run a Browser with slow JavaScript (say, Internet Explorer), i notice that it sometimes does not "feel" fast.
Also, if you are running custom code on it: Make sure to dispose your SPWebs after use, that can up a lot!
There is a known issue with initial requests once an IIS application pool has unloaded the SharePoint resources or recycled itself where the spin-up on a new request is very slow.
Details about why that happens and how to fix it can be found here; SharePoint 2007 Quirks - Solving painfully slow spin-up times
Andrew Connell's latest book (Professional SharePoint 2007 Web Content Management Development) has an entire chapter dedicated to imporving performance of SharePoint sites.
Key topics it covers are Caching, Limiting page load (particularly how to remove CORE.js if it's not needed), working with Disposable objects and how to work with SharePoint querying.
2 really good tricks I've got are to use the CSS Freindly Control Adapters to generate smaller HTML for the common components (menus, etc) and setting up a server "wake up", so when IIS sleeps the app-pool due to inactivity you can reawaken it before someone hits your site.
Are you running on virtual or physical servers? We found that it is significantly faster on physical servers. Also, check the disk performance - if you are running the servers from a SAN it might be a sign that your SAN is over utilised.
Microsoft has released a white paper on this very issue.
How Microsoft IT Increases Availability and Decreases Rendering Time of SharePoint Sites Technical White Paper Published: September 2008
Download it from here.
To investigate SharePoint performance issues, I would try these things first, in that order:
The three main major components of SharePoint setup is SharePoint Server (the one which runs WSS/SPS services), SQL Server DB and IIS.
You said you have decent power for your SharePoint services and I assume IIS would definitely be on a good machine.
Usually SQL Server setup that hosts the SP related DBs that would slow down the page loads. I would want you to take a look at your whole SQL Server related performance counters and you might want to tune these DBs too (which includes OS Server/Stored Procedures/Network, etc)
Hope this adds to your checklist of things you want to take a look at.