Working with FireWire Drives

Posted: May 15, 2011

[ This article was first published in the March, 2005, issue of
Larry's Monthly Final Cut Studio Newsletter. Click here to subscribe.
Updated April, 2005. ]

 

This technique grew out of a message sent by Christopher Warren, who asked:

I don’t know whether you have ever talked about using Firewire hard drives for MiniDV with Final Cut Pro:

  • Whether to partition or not
  • I have problems with them starting up from sleep mode
  • How many drive can you daisy chain together
  • Should you group different sizes or brand names together or keep them separate
  • Whether to turn off journalling for a speed bump
  • Cooling issues
  • And any other issues that would effect performance

Larry replies: Based on my conversations with a variety of hard drive and RAID vendors, here are my suggestions.

NOTE: By the way, if terms like RAID 0 or RAID 1 confuse you, read this short explanation of how RAIDS are defined.

A FireWire Preamble

First, Firewire is a perfectly fine technology to use for capturing DV video. However, there are some things you need to be aware of in order to maximize your success.

When you capture DV, you are simultaneously capturing both video and audio at the rate of 3.75 megabytes per second. An hour of DV material (audio and video) takes 13.5 gigabytes to store.

While 4 megabytes a second may not sound like much — yes, I rounded the number up — it’s actually pretty demanding on a hard drive, because the drive needs to deliver 4 MB/s second after second, minute after minute. For this reason, you need to get a FireWire drive that meets the following three criteria:

  1. It needs to spin at 7,200 RPM, or faster
  2. It needs an 8 MB cache
  3. It needs an Oxford 911 chip for FireWire 400, or,
  4. An Oxford 922 chip for FireWire 800.

If your drive meets those three criteria, it is reasonably likely to work well with Final Cut.

But wait, there’s more.

In an ideal environment, FireWire 400 transfers data at 50 megabytes per second. However, while that’s the maximum data transfer rate of Firewire 400, the hard drive inside the case is nowhere near that fast.

Generally, a single external FireWire hard disk moves data at between 20 and 25 MB/second. SATA drives will be somewhat faster. Writing data, by the way, is always faster than reading. You can increase this transfer speed by using a RAID, but for this discussion we will limit our comments to single drives.

Every stream of video on your timeline requires roughly 4 MB of data each second. So, doing a dissolve means that during the dissolve, the hard drive needs to send 4 MB/s for the outgoing shot and 4 MB/s for the incoming shot. If you have three images on screen at once, that’s 4 MB/s times three.

Complicating this process is that FireWire is a very “chatty” protocol; the drives spend a lot of time talking to each other, and the computer, reminding each other they are still connected and making sure everything is functioning OK.

For this reason, I allow 25% of total data throughput for the computer and drives to exchange FireWire protocol information, separate from any audio or video material.

On G-4′s, I reserve less, on G-5′s I reserve more.

Wrapping up this preamble before answering your questions is that the fuller a hard disk gets, the slower it plays. And, in fact, you can so fill up a hard drive that it neither reads, nor writes, data.

While Phil Hodgetts and I have agreed to disagree on how full, exactly, is too full, I recommend you keep your hard disks no more than 90% full. The world will not end if they get fuller, but they will start to slow down.

Getting Down to the Questions

So, with that as an introduction, here are my answers to your questions:

1) Should you partition a drive? No. In the past, partitioning was necessary in order for applications to work properly. With today’s operating systems and applications, there is no performance advantage to partitioning. As the engineers at Huge Systems told me, partitioning is neither good nor bad. In the future, though, partitioning will decrease system performance.

The only time I recommend partitioning is when you want to create a backup to your boot disk. However, never store media on one side of a partitioned drive with the operating system and applications on the other. That is a recipe for dropped frames.

2) Sleep mode, by definition, tells your hard drives not to spin. If they are not spinning, they are not sending or receiving data from your system. In other words, sleep is bad. Go to System Preferences > Energy Saver and set sleep to “Never,” and UNcheck the two check boxes. Unlike people, your hard drives will not die for lack of sleep.

 

3) How many FireWire drives should you daisy chain together? The FireWire spec says 63. Sigh… I don’t recommend that number. I have a few clients with 6-12 FireWire drives talking to a G-4. However, G-5s seem to have a problem when they talk to more than 4 FireWire drives. In my opinion, if you need that much storage, you are much better off with a RAID than a collection of FireWire drives. I would not recommend more than a dozen or so drives to be attached to any system.

On the G-5 in my studio, I have two internal drives and three external FireWire drives and they all seem happy.

4) Should you group drives by size or brand? First, there’s no way to “group” drives. FireWire is just a bus — all the devices “see” and “talk” to everyone else. There is no sectioning, or grouping. Keep in mind that you want to keep your FireWire cables as short as possible. When the total length of FireWire cable between all drives exceeds 15 feet, data errors can start to result. If you need to move drives a long way from the computer, be sure to use amplified FireWire cables.

Second, a FireWire device has no preference for a specific size or brand. So you won’t need to worry about that.

5) You should turn journaling ON for your boot disk, the one with the operating system on it. You should turn journaling OFF for any hard disks that you plan to use for capturing media. If you don’t know how to turn journaling on or off, here’s an article that explains it.

 

http://www.larryjordan.biz/articles/lj_journaling.html

 

6) Cooling issues. As long as there is air flow around the drive, you won’t need to worry about cooling. If you are putting all your drives in a box to keep the noise down, you’ll need to make sure the box stays cool. (Smoke curling up from the back of your drive is simply nature’s way of telling you that your data is now toast…)

 

However, if the temperature in the room is comfortable enough for you to work in your shirt sleeves, your drives will do just fine.

Update: At the 2005 NAB, I learned that it is generally not a good idea to put your deck or camera at the end of a FireWire chain. The reason is that many, but not all, decks and cameras communicate at FireWire 100 speeds. This means that your whole FireWire bus slows down.

If you are experiencing speed issues, disconnect your camera or deck and see if things improve. (By the way, the Sony DSR-11 is a FireWire 400 device… I checked.)

Hope these answers help.

Your thoughts are welcome



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