I'm setting up a new web/database server that will perform a lot of read/write operations. So I want to use a RAID controller and use RAID 10. I need some help to decide what kind of hard drives I should get? VelociRaptor? SAS? (Is it worth the cost?)
If you expect your disks to be used (i.e. actual significant activity) for more than 30% of the time then go for proper enterprise SAS disks as >95% of disks only have a 30% "duty cycle" and going over this will impact their lifespan and potentially the support you get from the manufacturer. I always use enterprise SAS disks (usually 15krpm ones) for DB work as anything less, in my experience, is money badly spent.
SAS - very expensive drives. Velociraptors - pretty much best bang for the buck. Question is - what do you need? you dont say at all.
I run a server with now 12 soon 16 raptors in 2 raid 10 groups (one 6 for hyper-v, one 6 for a sql server alone), 300gb model, and I am VERY happy with them.
But then I need them.
Your "a lot of read/write operations" is like "I drive a lot". WHat is driving a lot per year for you? Hint - I sometimes do 10.000km a month. It really depends on point of view.
In general, Raptors have good IO and are better per dollar than SAS drives. If you need a LOT of iops, then nothing beats higher end (Intel) SSDs - hands down, but you pay a LOT per gb. DO you need them? Depends. What is a lot of operations for you?