What's the right RAID Controller for my Dell Server?

I don't quite understand the significance of differences between the various Dell RAID controllers for my scenario, it would be great if you guys could help me choosing the right one. I don't want to burn money by buying something for no reason, but at the same time ensure that I'm getting what I need.

For my Dell R710 2U server with 6x 146 GB 15K RPM drives, I have the choice between the following controllers:

• SAS 6/iR Integrated, x6 Chassis [automatically included]
• PERC H200 Integrated RAID Controller [adds $199]
• PERC 6/i SAS RAID Controller, 2x4 Connectors, Internal, PCIe, 256MB Cache [adds $299]
• PERC H700 Integrated RAID Controller, 512 MB Cache [adds $499]
• PERC H700 Integrated RAID Controller, 512 MB NV Cache [adds $699]
• PERC H700 Integrated RAID Controller, 1 GB NV Cache [adds $799]

In case it matters, the server is going to run Windows Server 2008 R2, SQL Server 2008 R2, and IIS, and basically host various websites with varying degrees of complexity and SQL activity.

I want to run 3 RAID-1 arrays (2 discs each), with the OS/TempDB etc. on the first array, SQL data on the second array, and SQL log on the third array.

Really appreciate your help. Thanks!

For Dell, "256MB Cache" means 256MB of battery-backed cache on the RAID card. This is the cache used by the card for I/O operations. It caches writes in this storage to re-order them for more efficient usage of your disk. The battery is there in case of power loss, the battery supplies voltage to the cache-RAM. I believe it lasts up to 2 days.

"512MB NV Cache" means non-volatile. I don't know exactly how Dell does it, but I strongly suspect it has a normal RAM-based cache. A super-capacitor on the card has enough juice to commit the cache to flash-memory in case of sudden power loss. This will survive a power-outage for a lot longer than a battery-backed cache.

1GB NV Cache just has more cache.

The amount of data you're slinging around isn't that large to multiple internal connectors is not that important.

If you trust your power environment very well, a battery-backed cache will save you some money versus the non-volatile cache option.