If you implement my backup philosophy in your own home or studio, you’re going to need three kinds of non-volatile storage. The first kind is your main disk storage. It should be fast, and large enough for all your images. The second is your backup disk storage. It should be equally capacious, but needn’t be fast. The third is your offsite image storage. I will discuss each in turn.
Main Disk Storage. This is the primary storage for your image collection. Your computer came with at least one internal hard disk. Depending on the size of that disk, you may be able to keep up with the growth of your collection of images simply by upgrading your computer every two or three years. If so, you needn’t worry about the details. If you find that you must add disk capacity, you have some decisions to make. The possibilities are:
Adding one or more internal hard disks. This probably the cheapest way to go, especially if you don’t value your time highly. You’ll need to find out if you have room for the disk(s), if there is adequate power and cooling capacity. You should also have a look at your motherboard and see what kind of disk interface it supports, and buy disks that are compatible with that interface. You may have several interfaces to choose from. If it’s a fairly new motherboard, it probably supports SATA, and you’ll want a SATA drive. It may not support the latest and greatest SATA version, so you might not get all the performance or which your fancy new disk is capable, but it will work. If all this sounds daunting, have a trusted repair shop do the work, or read on for less invasive alternatives.
Adding one or more external hard disks. External hard disks contain the same disk drives as the internal ones, but they come packaged in their own cases, with their own power supplies, and have different interfaces than internal drives. The cost premium for the extra hardware is surprisingly low. I recently saw a Seagate 3 TB raw hard disk on Amazon for $260. The external version was ten bucks cheaper, and came with a backup program. There are three interfaces commonly employed by external drives: USB 2.0, USB 3.0, Thunderbolt, and eSATA. Maximum transfer rates are 480 Mb/s for USB 2.0, 5 Gb/s for USB 3.0, 10 Gb/s for Thunderbolt, and 6 Gb/s for eSATA. You may be suspicious of these rates; I know I was. In my testing, I was pleasantly surprised to find that USB 2 and eSATA were capable of sustained disk transfers of the large files that comprise photographic images at rates within 20% to 25% of those quoted.
Adding a network file server. There are two types of network file servers. The traditional way to build one is to take a more-or-less ordinary computer with an Ethernet port, and put a lot of disk storage on it. Most desktop operating systems support some form of file sharing, so you don’t need server software. If you decide to use server software, you will gain enhanced management options. You can buy a computer with the idea of making it a file server, or you can upgrade an old computer that you happen to have lying around; the file server role makes few demands on computer hardware than acting as a desktop machine.
An alternative to using a standard computer as a file server is to buy a box designed from the ground up as a file server. These devices are referred to collectively as Network Attached Storage. A NAS box will typically be smaller, cheaper, more reliable, and less power-hungry than a file server of similar capacity built from off-the-shelf computer parts. You can buy a 15 TB NAS box for between $300 and $1000 more than the cost of the disks alone. No matter which way you obtain your file server, you will have to live with the performance limitations of network access. You want your file server and your workstations to support gigabit Ethernet, which offers raw transfer rates of 1 Gb/s. You will probably obtain rates of about 700 Mb/s for photographic image transfers. That means that a 40 MB image will load in about half a second, a 500 MB image in about ten seconds. You may want to copy images from the file server to your hard disk in bulk, work on them, and copy them back when you’re done.
Backup Disk Storage. My principle tenet for disk-based storage is that no single hardware failure, few double hardware failures, and no foreseeable software error should cause loss of data that cannot be recovered in a few minutes of reconstructive work. This means that onsite data must be stored in at least two places, and I recommend three or four. The candidates are the same as for online storage: internal hard disks, external hard disks, and network file servers. However, we evaluate them differently when talking about backup. I think internal hard disks are a non-starter for backup. There are too many things that can go wrong inside a computer that can take out data on a hard disk, and many of those things can take out data on several hard disks. If you must have your backup storage on the same computer as your primary storage, at least put it on an external drive with its own power supply. If your primary computer has a meltdown, you can get running quickly after you replace it by just hooking your external hard disk up to the new computer. You get even more isolation from a single failure with network attached storage. Don’t worry about having a fast interface to your backup hard drive; the actual backups will be done in the background, possibly when you’re asleep, and you won’t care how long they take.
Offline Image Storage. The traditional way to back up disk drives has been magnetic tape. Unfortunately, magnetic tape has not advanced as rapidly as disk storage in the past fifteen years and is now the backup media of choice for only systems with hundreds of terabytes of storage. Let’s consider backing up a single 4 TB drive. A 5 TB Oracle/StorageTek T10000C tape drive will cost you thousands of dollars, the cartridges cost almost $300, to back up a drive that costs less than that. You can get an LTO drive for less, but the cartridges cost more per byte. What about optical discs? You already have a CD writer, but it would take more than six thousand CDs do that backup. Even if the CDs were free, you wouldn’t go to the trouble. You could back up the drive to DVDs, but it would take 800 disks. A BluRay read/write drive; even with 25 GB per disc, would take160 discs do to our backup.
In my opinion, the cheapest and most convenient backup for hard disk systems is – wait for it – hard disks. Have one or two external 2 or 3 TB hard disks on a computer and make sure that this storage always contains a backup copy of all your images. Have an identical set of disks in reserve. Every month or so, take the external disk drive(s) to an offsite storage facility like a safe deposit box, and bring the reserve disk(s) home. The cost to back up our 4 TB disk? Less than three hundred bucks, a bargain. Be careful when you transport your disks; they’re not as fragile as they used to be, but you still don’t want to subject them to any but the most gentle of mechanical shocks. You should consider rubber or plastic cases that reduce the effects of shock and static electricity.
One possibility for offline image backup is Internet data storage. As a way to make your images accessible wherever you are, this could be a winner. However, your bandwidth to the Internet may be a problem, not so much for uploading the data, but for recovering it in the event of a disaster. At T1 speeds, 1.5 Mb/s, it would take a month to restore 4 TB of data. If you tried downloading this much data continuously over a DSL or cable line, you’d probably get a notice from your ISP requesting that you take your business elsewhere.