Should photographers use RAID arrays for image storage?
by Ralph Paonessa
Published February 28, 2007
Question: I'm planning to expand my disk storage to accommodate all the image files from my digital cameras. What do you think of RAID storage options?
Answer: I would recommend against RAID for most photographers. RAID, which stands for Redundant Array of Inexpensive (or Independent) Disks, combines several hard drives into a single unit. These drives appear as a single disk to the operating system, but different configurations (known as RAID levels) serve different purposes.
RAID 0 splits or "stripes" data between two or more drives for faster read/write speeds. This type of speed is often required by video editors, especially in HD or raw video formats, where tremendous amounts of data must be transferred in real time. But photographers generally don't benefit from these speed increases.
RAID I simultaneously copies or "mirrors" the same data onto multiple drives, for redundant, immediate backup. The drives are often "hot swappable," so that if one drive fails, a mirror drive takes its place for virtually no data downtime, and a replacement drive is "rebuilt" in the background.
RAID I is valuable to large enterprise systems like banks, online reservation systems, or other large servers that must provide 24/7 uptime. But this is not the type of data backup problem that you as a photographer probably need to solve.
For most photographers, RAID is an unnecessary complication. There are better ways to back up your images.
Backing up your image files is essential. Suppose your camera creates 10 MB raw files. A single 250 GB hard drive can hold 25,000 images. That's the equivalent of almost 700 rolls of processed film—which once would have cost you around $7,000, and more importantly might represent years of shooting. And if these represent your best images after discards, you've concentrated even more value and time onto that drive.
Multiple hard drives are affordable
Today you can get high-end 250 GB external hard drives for under $150—a real bargain in the scheme of things. You can move up to 500 GB for under $200. You can get several of these drives for storage and backup. If you're comfortable configuring computer hardware, you can buy internal "bare" drives for even less. For these you need open slots and interfaces in your computer case, or external boxes that hold multiple drives and connect to your computer via USB 2.0, FireWire, or eSATA connections, among others.
A good practice is to immediately back up your data, and maintain at least 3 copies. Store at least one copy offline in a physically separate location, to guard against fire or theft. Keep another set of backup drives attached to your computer for periodic (daily or weekly) backups.
Backup to write-once media as well
I also recommend making an additional backup copy (or copies) on write-once media like DVDs or CDs. (I confess I haven't done this, but I'm planning on buying a DVD burner and burning several hundred DVDs soon.) Once the data is written, it is immune to corruption from subsequent viruses, software and hardware glitches, or human error that can inadvertently delete or destroy years worth of data on a hard drive in a few keystrokes.
I find CDs and DVDs hugely inconvenient for storing any images that I might ever want to access. I don't want to have to page through hundreds of disks to find the image I need, even if a good database tells me exactly which disk it's on. I will simply put them away somewhere safe in case my hard drive data gets corrupted (and the corruption gets copied onto all my backup drives before I realize it).
One concern about CDs and DVDs is how long they will last. Your best bet is to avoid bargain writers and media; this is not the place to economize. DVDs that use gold are gaining popularity as "archival"—although this is ultimately a marketing term with no guarantee of longevity. Still, I would recommend spending extra for gold DVDs for archiving your valuable images. Current brands include Delkin, Verbatim, and MAM-A (Mitsui).
Also, do not use rewritable media here (i.e., use DVD-R or DVD+R and not DVD-RW). The rewritable disks, besides costing more, seem more prone to problems. Ditto for dual layer, versus single layer. Finally, high-capacity Blu-ray and HD-DVD disks and burners are now available. (I'm waiting for a clear winner to emerge and prices to drop.)
Diversify your storage
As in the stock market, it pays to diversify when storing and backing up your data.
Use both hard drives and CDs/DVDs to gain the advantages (and cover yourself against the weaknesses) of each. And store at least one copy in a separate location in case of physical disaster or theft.
Back to RAID: There are other levels of RAID, but I don't see it as the storage method of choice for photographers. I've heard of some photographers who dedicate two disks to a striped RAID 0 array solely as a faster Photoshop scratch disk. If you have a couple smaller drives laying around (e.g., because you upgraded to larger drives), you might experiment with this. But if you're slowed down by constant scratch disk access in Photoshop, you may be better off investing in the maximum amount of RAM your computer can handle, which will reduce the need for Photoshop to go to the scratch disk. (Increasing your RAM is a generally very cost-effective way of boosting computer performance.)
Whatever your approach, take image backup seriously.
Hard drives inevitably fail. Stuff happens. Years of work can be wiped out in an instant if it's all stored on a single drive. Hard drives and DVD burners have come down so much in price that it makes sense to invest a little bit more money to safeguard the images you spent thousands of dollars and days and years of effort to create. Do it now.
You can learn more about RAID at Wikipedia.