Will Head
With movie files taking up so much space, video editing has hefty storage requirements, but choosing which type you need can be a minefield.
No matter which video format you shoot and edit in, there’s no getting away from the fact that video eats up storage. One hour of standard-definition DV occupies 13GB of space, which means a 500GB drive will be full before you’ve hit 40 hours of footage – and that’s assuming there’s nothing else on it.
Move into HD and you’re looking at around twice as much space per hour, possibly more. HDV may have the same data rate as DV, so one hour still occupies 13GB, but it uses Mpeg-2 compression to do this, which isn’t ideal for editing. This means you’ll inevitably end up transcoding your footage into a more edit-friendly format before you start hacking away at it.
If you’re using a Mac Pro setup, adding enough storage is less of a problem: you can configure a machine with up to 8TB of internal storage, thanks to the four internal drive bays on offer. That’s enough for more than 600 hours of standard-definition material, which is 25 days’ worth.
The 27in quad-core Core i7 iMac may look pretty well specified for video editing on paper, but with just one drive slot available, you’re looking at a maximum capacity of 2TB. If you can avoid it, it’s best not to use the system drive to store your video files, as it’s already in constant demand running Mac OS X. Add in the fact that once you’ve accounted for the size of the operating system and applications, bringing the free space for video down to around 1.7TB, and it soon looks like the hard drive could be the limiting factor.
If you’re planning to edit on the go, then mobile storage options are even more restricted. Again, you’re limited to a single internal drive, which means storing your video files on the system drive. However, the current maximum you can pack inside a MacBook Pro is 500GB. Even if you keep the OS and apps to a bare minimum, you’re still only looking at around 350GB of free space for video, which is only enough for 25 hours of standard-definition footage.
This also assumes that you’re the only one working on a particular project at any one time. Even if you’ve got a Mac Pro stacked with 8TB of storage, if someone else needs to access the files stored on it at the same time, then you won’t be able to use the machine until they’ve finished.
Packing individual machines with masses of storage also create other problems. For a start, it’s not very efficient to have multiple copies of the same source footage sitting on every machine you’ve got. Not only does it take a long time to move files from one machine to another in the first place, but it also means that storage may be used up that doesn’t need to be.
Backing up all the machines also becomes problematic because the more storage there is in each one, the more there is to back up each time, which takes longer and requires greater backup capacity.
Even if you could continue adding extra hard drives to a machine as it filled up, it wouldn’t be the best solution to the problem.
The better option is to use some sort of storage pool that allows all users to access the same files. This is more complex than just setting up a network, though due to the large file sizes involved and the need for fast access, otherwise you won’t be able to use it for video editing.
There are many different options available and which one to go for generally comes down to which Macs you want to be able to access the storage, how many users you need to work with and how much money you’ve got to spend.
At the top end of the market is a storage area network (San), which is basically a group of disks attached to a very fast pipe – usually Fibre Channel. While a San will offer the best performance for a group of Macs, setting one up can be incredibly expensive – in some cases considerably more than the machines to which you’re connecting it. You will get extremely good performance, but it’s usually overkill for small teams. If it uses Fibre Channel, then you can only use it with Mac Pros as well, since iMacs and MacBook Pros don’t have the expansion slots necessary for a Fibre Channel card.
At the other end of the market you have direct-attached storage or Das, which is basically a drive connected to your Mac – for example, a FireWire external drive. This is one of the cheapest and easiest options available and solves a couple of the problems, such as not having multiple copies of data lying around, and it’s easy to back up. While it can be a shared resource – just unplug it from one Mac and plug it into another – it’s not something two users can access at the same time.
The connection between the drive and your Mac will also dictate how fast the storage is and which machines you can use it with. While eSata is the fastest, you’ll only be able to use it with Mac Pros and 17in MacBook Pros. FireWire 800 isn’t as speedy, but you can use it across all of Apple’s current range of machines. Finally, if you’re looking for something mobile, then you’ll need a drive that can be powered from your MacBook: if you’re working in a field, a drive that needs mains power is useless.
Given that all Macs have a Gigabit Ethernet port, you might think a network-attached storage (Nas) drive would fit the bill. This is basically a hard drive with a network connection, so you can share files between Macs on the same network. While Gigabit Ethernet is fast enough for many applications in principle, the overhead of routing all the file information over the network cuts down the speed to such an extent that it isn’t really a practical solution.
There is one option that sits in the middle, however, providing many of the benefits of San but without the high cost, is simpler to share files between multiple Macs than Das and is faster than Nas. Network direct-attached storage (Ndas) is similar to a Nas drive, but while it uses the physical Gigabit Ethernet connection, it employs a proprietary system rather than TCP/IP to send data over the network. The result is speeds similar to Das at a fraction of the cost of implementing a San.
The Iocell NetDisk 351UNE is a bare enclosure into which you can fit any Sata disk and sells for just £69.99. It has USB, eSata and Gigabit Ethernet ports, and uses Ndas when connected via the network. Unlike a regular Nas drive, which just appears on the network, you do need to use the supplied utility to mount the device. Once mounted, it appears as a Das drive to the Mac, so you can treat it just like a regular disk. The downside is that only one machine can have read/write access to the drive at a time; any other connections must be read only. However, copying new footage onto the drive will be a less-frequent occurrence than accessing the files in your video editing application, so this problem is more of a minor inconvenience than a deal breaker for video work.
To get an idea of performance, I pitted the Iocell NetDisk against a regular Nas drive and also a G-Technology G-Raid mini. The latter is a 1TB Das drive with eSata, FireWire 800 and USB 2 ports, making it ideal for portable video work. As its name implies, it’s a Raid device so there are actually two disks inside. You can configure it to use both of them together for increased performance or to mirror each other for extra protection. It can also draw its power from the FireWire connection, so you can use it somewhere with no mains power.
AJA System Test lets you simulate read and write tests using a variety of video frame and file sizes. The Sweep Video Frame Sizes option tests each frame size one after another and I repeated this for 128MB, 256MB, 512MB and 1GB file sizes. I tested the G-Raid mini in both Raid configurations and the NetDisk once with only one Mac connected, and again running the tests while a second Mac was simultaneously playing back an HDV video file stored on the drive.
Averaging out the results across all tests, the Nas drive achieved a read speed of 7.9MB/sec and write speed of 2.1MB/sec, which is pretty pitiful and isn’t sufficient for video use. The G-Raid mini connected via FireWire 800 in Raid 0 configuration achieved 79.9MB/sec and 69.8MB/sec for read and write respectively. In the mirrored Raid 1 setup, it scored 77.7MB/sec and 64.9MB/sec. Both these speeds are fine for editing DV, HDV or even ProRes Proxy.
The NetDisk managed an average read rate of 62.2MB/sec on a single connection, dropping to 55.6MB/sec when another Mac was also accessing the disk. Write speeds were 75.3MB/sec singly and 65.4MB/sec with dual access. Again, these rates are fine for editing DV, HDV and ProRes Proxy, even with more than one Mac accessing the disk at the same time.
If you need fast, portable storage that you can easily switch between Macs while you’re mobile, then the G-Raid mini is definitely up to the job. For an office setup, a San would obviously be the better option, but if you’re strapped for cash and can live with its slight limitations, the NetDisk is worth investigating while you save up your pennies.
