aic79xx and global_tag_depth

[slam_head]

I've been trying to tune a system in which I have 24 drives on 6 chanels. I was have a problem where drive would drop out during heavy read-write operations. I dropped the global_tag_depth down to 16 from 32, and it looks like that has solved my stability problems but at a heavy performance hit. My question is does the global_tag_depth need to be in powers of 2? If so is there anything else I should try to balance performance and stability?