No idea on the disk types to choose, go with the fastest throughput you can.

Do not use R5, except maybe for backups. http://www.baarf.com has good reasons to stick with R1 or R10.

The daily transaction count doesn't matter, it depends on how it's distributed. 30M in one hour and 0 the rest of the day is different than 30M evenly spread.

You want to separate things out that have contention. If you have a busy write/update server, then you might want an R1 array for your logs. If you have heavy queries, then you might want separate R1/R10 arrays for certain tables or indexes away from data.

Memory is probably more important, so be sure that you have a high buffer cache hit ratio no matter what the disk is.