Daisy-Chaining Firewire Drives

I've identified some serious problems with drive performance when daisy-chaining at Link TV. Daisy-chaining is a way to hook up multiple devices (in this case, hard drives) to one port (in this case, firewire). Firewire is theoretically supposed to handle 63 devices in one chain. I've been daisy-chaining firewire drives to FCP for 6 years, but Apple doesn't consider this a supported setup for editing.

Well, I've finally run into some real problems with daisy-chaining firewire drives. I've been seeing some real poor performance out of drives. Symptoms include aborted file transfers, the hanging up of the system when a movie is played, and very slow write performance. I think I've figured out the cause. There seems to be some problems mixing certain drives in one chain. In particular, I think certain drives from Other World Computing (OWC) don't play well with other drives, in particular drives from G-Technology, like the G-Raid. OWC makes the Mercury Elite Aluminum Pro drive and RAID. G-Technology makes the G-Drive and the G-RAID.

The workaround I've identified is to make sure that a chain of drives is all from one manufacturer. For example, in our dub room setup, the G-Drive is on a firewire 400 port and the OWC drives are on the Firewire 800 port. Our computers in Edit 2 & Edit 3 have PCI cards that add 3 firewire 800 ports. So there are a lot of ports there, and it's easier to segregate OWC and G-Technology drives.

So far I've been able to diagnose this problem by checking the read/write performance of drives when I think there is a problem. I've been using the SpeedTools utility QuickBench to check drives by running the Extended Test with 20-100 MB files. If you are seeing a drive read or write at 10 MB/sec or slower then something is seriously wrong. If you think daisy-chaining may be the issue, a quick way to check is to unplug all the drives except the one that is acting up. If you then retest the drive and performance is way up, then you probably are dealing with a problem with daisy-chaining.

I've seen other, less serious problems with daisy-chaining. My write speeds on G-RAID's drops by about half when they are daisy-chained. This is a nuisance, but it's never really interfered with my work. I'm not doing any capture of 10-bit video or anything too demanding luckily.