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Welcome Back. In this issue, we'll be talking about 3 types of Hard Drive's and their interfaces that are being used in Editing Host Computers.
First things first.
If you're using Avid Xpress DV or Pro WITHOUT Avid MOJO, you're really only editing in one of 2 Video Resolutions:
1) DV resolution – About 5 Minutes of Video per Gigabyte of Storage.
2) 15:1s resolution – A Single Field resolution that is give approximately 6 times the storage capacity of DV resolution.
The good news is, just about any hard drive on the market will handle multiple streams of DV resolution in real-time. So, what about 15:1s? Does that mean that you'll have 6 times the performance with 15:1s over DV?
No. You see, displaying multiple streams of Video in Real-Time is not JUST a function of your Hard Drives speed and through-put. You CPU is also taxed during playback because your editing software actually needs to decode the codec that the stream is encoded in. DV is actually a codec, albeit a HIGHLY optimized one. 15:1s, on the other hand, does eat up a fair amount of CPU cycles – In most cases, more than decoding a DV compressed stream.
So, the question of performance is also related to the power of your CPU. Having said that, if you're running just about any class of Pentium 4 processor, you should be able to decode at least a few streams of DV in real-time. You might need a 2.0GHz or above processor to get more than one stream of 15:1s.
Hard Drive Storage capacity has not only skyrocketed, it's also as inexpensive as it's ever been. In fact, you can get about 1 GB of storage per dollar you spend.
Let's talk about the 3 types of Hard Drives and their interfaces that are on the market today.
1. ATA/IDE Drives
The most common type of Drive/Interface, the IDE/ATA drive has established itself as the workhorse of the computing industry. The latest drive interface, known as ULTRA ATA has the capacity to burst up to 133MB per second. While there is no singe UATA drive that can transfer that much data, the point of the spec is that if you configure several UATA drives into a RAID 0 Array, you could get pretty close.
Experts will argue that over the bandwidth needed to stream uncompressed video, but if you consider that every frame of video is about 900Kb, and multiply that by 30 Frames per Second, you get a value of about 27Mb per second for uncompressed video.
Now, a GOOD UATA Drive can sustain around 30MB per second of through put. Not bad right?
Well, the truth is, you really want more than 10% of data headroom, and with the figures above, you're cutting it pretty close.
Now, if we use a RAID (Redundant Array of Independent (or Inexpensive) Disks), we can nearly double the bandwidth of our data pipe by having both hard drives act as a single unit.
In the case of 2 Hard Drives Striped together, we're now looking at a RAID level 0 through-put of closer to 60MB per second, which is more than enough to handle a single stream of uncompressed video.
The point is, if you're editing DV which maintains a 5:1 compression ratio over uncompressed video, you don't need to introduce RAID striping into your systems Hard Drives.
So, why should you even consider another format (Like SATA or SCSI) or a RAID array?
UATA/IDE is known to use a fair amount of system resources when the drives are being accessed. In fact, in some cases of activity, the CPU may be taxed enough to cause your software performance to suffer in a dramatic way.
Enter RAID. A true HARDWARE RAID, that is, one that is managed by a separate hardware card or subsystem on your motherboard takes the burden of Hard Drive Access and management away form the CPU. So, in addition to the increased Bandwidth that a RAID offers, it also frees up your systems resource.
The same can be said for SATA Drives.
You see, the “S" in SATA stands for Serial. Serial is the same kind of remarkably flexible interface that's used in USB and Firewire. ATA/IDE drives are based on the “Parallel" interface. That's the same sort of interface that Printers used to use. Ultimately, a Parallel interface is slowwwww. In fact, in order to get a Parallel interface to work at UATA speeds, it needs over 80 separate lines running to it. You've probably seen an ATA Ribbon cable, its about 2 inches wide and flat.
Now, compare that to a SATA interface. It's one cable thats about the size of a Firewire Cable. That's it…
The benefits of SATA based drives are many. First, there's no configuration issues. Just plug in the slim interface cable and give the drive some power and you're up and running. Second, there's no “Master – Slave – Cable Select" jumpers to configure with a SATA drive. And lastly, the top end of SATA-1's through put is a very generous 150MB per second.
Manufactures also seem to be taking advantage of this new interface standard and are building their hard drives to take advantage of SATA's new, larger data pipe. In fact, some SATA drives are now reported to have almost a 20% better throughput than their ATA counterparts. That's good news for data hungry video applications.
The last word on SATA? According to the web site www.tomshardware.com, SATA RAIDS have “Sounded the death knell of SCSI".
SCSI Interface.
The SCSI interface has long been the bulletproof solution for Enterprise and Mission Critical Data Applications. In fact, SCSI is so reliable and it's data pipe is so large that it is still used broadly in most uncompressed video editing solutions, and with the exception of Apple's Xserver, is always used in High Definition Video applications.
The thing is, it's expensive. Very expensive. The average SCSI controller card will run you nearly $300, and the drives themselves are sometimes 200% more expensive than their ATA or SATA counterparts.
However, SCSI has been in the Video Editing game a long time, and the interface, besides being very difficult to configure, and the drives running at toaster oven temperatures, SCSI seems to be the defacto standard for Turn Key Hardware based solutions.
Again, if you were editing DV, SCSI would be overkill for your application. But, if you see multiple streams of uncompressed video, or a migration to High Definition video with another software application, SCSI may be your only solution, at least today.
Keep and eye on SATA – all indicators point towards this standard reigning supreme in the next 18 months.
Okay, here are some Hard Drives that I use in each one of the performance categories.
Just as a side note, all of the non-SCSI drives here are at least 7200 RPM with a 8MB cache buffer.
BIG - Maxtor 160GB EIDE HD 7200/8MB/9.3/ATA-133
At a fairly beefy 160GB, this is one of the fastest ATA dives around. Maxtor's truly represent a high standard of both performance and value in the ATA market. However, they are on the nosey side, so be prepared to have some additional sound emanating from your PC.
For more detailed information, follow this link:
http://www.likeapromedia.com/ata.html
BIGGER - Hitachi 250GB Serial ATA HD 7200/8MB/8.5/S-ATA-150
A whole quarter of a Terabyte on one hard drive. These are truly good times. This monster-capacity drive will hold nearly 21 hours of DV quality video. 21 Hours… They are also rip snorting fast, and are some of the quieter large-capacity drives on the market today. They also feature the SATA interface…
For more detailed information, follow this link:
http://www.likeapromedia.com/sata.html
BIGGEST - Hitachi 73GB 15K RPM U320 SCSI 80 Pin Hard Drive
What a monster! This disk spins at 15,000 RPM, nearly 2 times faster than it's SATA or IDE counterparts. With it's SCSI U320 interface, the maximum theoretical through put is 320MB PER SECOND! Be warned, this HD sounds like a dremel tool and will keep your coffee warm for hours.
For more detailed information, follow this link:
http://www.likeapromedia.com/scsi.html
The wildcard – FIREWIRE DRIVES.
It's important to keep in mind that a FIREWIRE Hard Drive is nothing more than an IDE/ATA drive that sits in an external case and has a Firewire interface attached to it. The advantage of a FIREWIRE drive is its portability, and the ease of use when attached to a plug and play Firewire enabled PC. But, just for kicks, we'll include on anyway.
As a word of caution, it's possible that if you have a Firewire drive and a Firewire camera or deck on the same Firewire channel, you will not be able to capture video.
Buslink 120GB Combo Serial ATA USB 2.0 & Firewire
I'll tell you why I love this drive, not only is it reasonably fast; it's got a USB interface. This is a fantastic feature. It allows me to walk media right over to an Animator and transfer it to their workstation, or output OMF files for ProTools for the whole show and let the music and sound effects folks to go to work. It's pretty quiet, too.
For more detailed information, follow this link:
http://www.likeapromedia.com/firewire.html
And so wraps another installment of “How to build your own Video Editing Host Computer".
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