I am in the process of designing an architecture based around a single Dell R910 server running Windows Server 2008 Enterprise.

I would like the server to have 8 RAID1 pairs of spinning disks, so I intend to implement:

Dell R910 Server Integrated PERC H700 Adapter with 1 SAS expander on each SAS connector (so 8 expanders in total) 7 RAID1 pairs of 143Gb 15K HDD, each paired on one connector using an expander 1 RAID1 pair of 600Gb 10K HDD, paired on the remaining connector using an expander

My main concern is not to introduce bottlenecks in this architecture, and I have the following questions.

1. Will the PERC H700 Adapter act as a bottleneck for disk access?
2. Will using SAS expanders for each RAID1 pair cause a bottleneck or would this be as fast as pairing disks directly attached to the SAS connectors?
3. Can I mix the disks, as long as the disks in each RAID1 pair are the same? I assume so.
4. Can anyone recommend any single-to-double SAS Expanders that are known to function well with the H700?

Cheers

Alex