[This article was first published in the March,
2005, issue of
Larry's Final Cut Pro Newslette. 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.
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:
- It needs to spin at 7,200 RPM, or faster
- It needs an 8 MB cache
- It needs an Oxford 911 chip for FireWire 400, or,
- 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.
This article is from "Larry's Final Cut Pro HD
Newsletter," a
very cool, FREE, monthly, Final Cut newsletter -- subscribe at Larry's
web site: www.larryjordan.biz.
Larry Jordan is a post-production consultant and an Apple-Certified
Trainer in Digital Media with over 25 years experience as producer,
director and editor with network, local and corporate credits. Based
in Los Angeles, he's a member of both the Directors Guild of America
and the Producers Guild of America.
Any references to trademarks or products are used for editorial purposes
only. Text copyright 2005 by Larry Jordan. All rights reserved.
