I'm just entering the realm of video and in the process of adding additional storage to support that. Current system consists of Mac Pro 2.8GHz (8 core) 8GB memory NVIDIA GeForce 8800 GT video card.
For storage I have four internal WD Caviar 640GB disks - configuration as follows:
Disk 1 - Partition 1 (100GB): Mac OS and resident apps
Disk 1 - Partition 2 (500GB): Backup for LOCAL
Disk 2 - Partition 1 (500GB): User data and apps including VMware machines
Disk 2 - Partition 2 (100GB): Backup for Mac OS (bootable)
Disk 3 and 4 I am planning a partitioned RAID 0
Partition 1: Striped RAID 0 for scratch disk
Partition 2: Striped RAID 0 for project files
My question is - How big should I make the scratch disk?
Current thought is 150GB partition - which effectively gives me 300GB scratch disk in RAID.
That least 900GB available for project data - which can backup nicely to 1TB external drive.
Is this too much? Too little? What is the rule of thumb for video scratch? In photoshop it is min. 5x image size - easy enough to figure out once I know what my largest image size is likely to be.
And yes - there is good backup strategy to compensate for RAID 0 risk. I opted for performance over safety in this regard. All disks backup to internal or external drives hourly, daily and weekly depending on the data.