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Information Today, Inc.

RAIDing the Digital Studio
Posted Feb 19, 2004 - October 2005 Issue Print Version     Page 1of 4 next »

There's nothing like a good day's shoot to fill up your workstation's storage. At the shooting stage, if the DV camera's tape is full, it's a simple task to pop out a cassette and drop in another. But it isn't that simple with workstation hard disk space. True to its name, fixed storage—when filled to capacity—can put you in quite a fix.

Of course, you're always free to add on. But consider what would happen if you just plugged in an endless succession of new hard disks to add space to your system. Since both FireWire and USB 2.0 support daisychaining drives together, it is conceivable that you could have an ever-growing set of disks laid out on the floor around your desk. However, you quickly realize that there are several problems with this setup.

First, every hard disk is its own entity to each application. So you have to go through disk after disk to locate your work files. Searching for data on even two disks becomes a challenge when time is of the essence. Second, if a file becomes too large for a single disk, you'll have to take time out to buy and add a larger disk to your system. Finally, even FireWire and USB channels lag in performance as the I/O burden becomes greater and greater and your workstation tries to talk to all these disks.

This means that rendering times soar, and you then have to face those oh-so-joyful delays in redrawing megapixel designs onscreen from virtual memory. All of which is the kiss of death for anyone doing post-production on budget or deadline, which means virtually anyone doing commercial video work.

This is where desktop RAID storage comes into play.

RAID is an acronym for Redundant Array of Independent (or Inexpensive) Disks. Time was when the "Inexpensive" was more of a joke than a genuine part of the acronym, because the RAID systems of the past were anything but inexpensive. In fact, RAID was primarily the province of the corporate server room where the system was patiently administered to by lab-coated gurus who knew how to appease the Storage Gods.

Now, thanks to the ever-decreasing price of hard disks and components, there are less expensive, pre-configured RAID systems for the desktop workstation that designers and editors can use and effectively ease the storage strain.

Have You Ever Seen the RAID?
RAID, in essence, is a way of making two or more hard disks appear as a single drive to the workstation. This "virtual" drive then can be far larger than any single drive making up the RAID set. Apple's Xserve RAID storage box, for example, can grow to almost three terabytes (or about 26 hours of uncompressed digital video footage at 30+ Mbps) with a full set of 14 drives installed. For OS X, however, all these drives appear as a single device, making management easier.

But RAID offers several more advantages beyond creating virtual disks that make it a compelling choice for the digital studio:
-Data protection
-Higher performance
-Fault tolerance
-Easier maintenance

Protecting data is the primary goal of RAID. Most RAID systems can readily recover from a single hard drive failure in the set. It only takes a single drive failure in a non-RAID protected workstation to demonstrate why RAID is important, given that the loss of even five or ten minutes of edited video might well be worth ten or twenty times that of any such storage system.

Equally important, RAID systems provide faster performance in reading and writing data to hard disks. That's because there is more than one drive available to answer the call when an application needs to record or retrieve data. This aspect of RAID is probably the most widely known advantage and thus a great reason to upgrade to RAID storage.

Another advantage comes along with protecting the data—fault tolerance. Since the RAID system can continue to work after a drive failure, there's no unscheduled downtime. This can again be a critical asset at crunch time when the video post team needs to meet a deadline.

Finally, replacing a failed drive in a RAID system is often only a matter of removing and replacing a snap-in module. This makes maintaining a RAID system much easier than storage drives on a conventional workstation. Compare that remove-and-replace process with that of recovering from a failed hard disk in a conventional workstation:
1. Power down the workstation
2. Open the case
3. Remove the hard drive cables
4. Detach the hard drive
5. Insert the replacement drive
6. Plug in the cables
7. Close the box
8. Reboot the workstation
9. Format the drive
10. Restore your data files from backup tape or optical disc

Any question which is easier or faster?

One last point—don't confuse RAID storage with a way to connect different devices to the CPU. There are RAID systems that support such connectors as SCSI, USB2.0, and FireWire. Internally, the box might have SCSI, ATA, or even SATA drives.

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