Hi
As mentioned, the performance requirement is hard to nail down, you could run Windows 7 on a PC with 512 Megs of ram but it wouldn't be fun to work on, this is how we make recommendations to our clients, it is not meant to be perfect from a technical perspective it is rather aimed at making things more understandable
With regards to the memory usage question: Memory is the best value for money performance gain on the server, as it is them able to use the memory instead of reading from the HDD which can be up to 3000 times slower than memory
You shouldn't restrict the amount of memory being used
From a practical perspective these are the recommendations we make to our clients, this was for a 15 user site, this was to be a combined SQL and Application server,
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1x Quad Core processor (Preferably 2)
– This directly affects the number of users that are able to work simultaneously, as the server is running SQL server as well as the NAV application server this means that each user will use a core when NAV is working on something for them and a code when NAV requests data from SQL to perform their task, adding additional cores is recommended as the user load grows and for more complex sites
12 Gigs RAM (More if possible here)
– The RAM is the single largest performance boost for a SQL server and continues to be until the amount of ram is greater than the size of the database + Temp tables, therefore 12 gigs is a good starting point but it can be grown later,
Expect the application servers to use up to 2 gigs of ram per 5 users, so this will provide 2 gigs of ram to the OS, 6 gigs of ram to 15 users and leave 4 gigs for the database, once the database grows beyond 4 gigs the amount of RAM in the server should be reviewed, this is dependent on the complexity of the site
(RAM is the best value for money performance improvement on a SQL server)
4x Hard drives (Speed of drives is much more important than the size of the drives)
– This becomes the next bottleneck after the RAM, as the performance of data retrieval from drives affects the speed at which the system can respond to client queries, a minimum of 4 drives are recommended in a RAID 10 setup,
(RAID 5 did not perform well on previous SQL editions, in the current editions it does now work however RAID 1+0 performs better when there has been a failure of a drive),
More drives (Added in sets of 2) will significantly improve drive performance, although servers have built in RAID controller, a separate battery backup raid controller is recommended for all sites but required for larger or more complex sites
Slower drives will also affect the performance of the processor as it waits for data retrieval from the drives
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Hope this helps make everything a bit clearer
Cheers
Nev