Jayson,

Your understanding of the expander usage, as I tried to convey, is correct.

Regarding the use of a single controller:

My own experience is only using a single controller (largest HDD array is 12 HDDs), and I would be concerned about the ability to manage all of the HDDs effectively (allowing me to create RAID groups using the optimal number of HDDs) without having to predetermine which HDDs would be connect to which controller (in a multi-controller scenario).

By the same token, there are valid reasons to justify multiple controllers (depending on number of HDDs);
- some controllers have a limit to the number of RAID sets/groups which can be created (I know that Adaptec controllers do).
- you may want a larger amount of cache memory than available from a given controller
- you may not need a cache controller for some HDDs
- you may want a fancy controller which does hybrid SSD caching, but only for some HDDs
- you may have exceptional throughput requirements which are more than the controller can handle (is only possible in large sequential transfers, or if you are building an array of SSDs)

Regarding Intel:

- Over the years Intel has created RAID controllers using their own chips or have simply rebranded/reused controller chips. Just because it says "Intel" doesn't mean that it is Intel"
- The most of the current Intel controllers (and the expander which you pointed out) are in fact based on LSI chips, so any controller based the same chip would perform the same and be as reliable
- There are other good/excellent RAID controllers available, all off which have good/excellent support. There are plenty of features which need to be considered beyond just the brand name of the controller (hybrid SSD RAID support is an important one -- could allow for lower SATA speed HDDs to be used instead of expensive high speed SAS drives -- for high read/low write applications)
- If you are concerned about warranty support than I would suggest that you simply buy a backup controller. If you run into a real problem, controller failure, the only way your are going to get up-and-running quickly is by simply swapping out the card, and worrying about the warranty return/swap on the card separately. That is what we have done for our 2 SAN/storage systems, waiting even 24 hours for a replacement is much too long for an outage.