Photoshop Tip: File Management and Backup

PHOTOSHOP TIP: File Management and Backup - Part Three
By Rich Seiling

When you make a backup, you are making a copy of your data--usually to something like a DVD-R disc or a backup tape. You have a lot of options when it comes to what media you want to use, and several factors affect that choice. If you need to backup 50-100GB of personal files where you only create a gigabyte of new files every week, you can get by with a simpler solution than if you need to backup up terabytes of data, and if you are creating tens of gigabytes of new data every day. To understand your needs and make a educated choice, let's explore the factors involved.

Speed
Every drive writes data at a different speed. Basically, you want to make sure that you can backup the necessary data in the allotted time. My experience is that the more time consuming the backup, the less likely you are to actually do it.

When considering speed, you need to understand that when you do a backup, you are really reading the data twice. If you are using backup software like Retrospect, the first step of a backup is to read the original and write it to the backup medium. The second step is to read the data back from the backup medium and compare it to the original to ensure that it was copied exactly. So, if you are backing up 4GB of data, the drive is actually going to have to read and write a total of 8GB of data--and if your drive can read/write 9GB per hour, your backup will take just under an hour.

Here are some estimated speeds for several devices:
2xDVD: 6.6 GB/hour
4xDVD: 13.2 GB/hour
8xDVD: 26.4 GB/hour
Sony AIT-1 drive: 9 GB/hour
Sony AIT-2 drive: 14-20 GB/hour depending on which medium is used

Even the slowest of these is good enough if you have 200GB or less of total data to backup.

Storage Density
Another important factor is storage density. This is one of the reasons we’re not talking about making backups to CD-Rs. At 700MB each, it would take about 72 CD-Rs to backup 50GB of data. Not only will that take up a lot of space, but it will mean a lot of swapping of discs, and you’ll have a lot of CDs to keep track of.

In general, you want media that lets you store a lot of data in a small amount of physical space. I think DVD-R and tapes are two good choices for backup media. Tape has the advantage over DVD-R in sheer compactness. Four Sony AIT-3 tapes that hold 100GB each take up the same space as about 12 DVDs in Tyvek sleeves. So, with tapes you can fit 400GB into the same physical space as 56.4 GB worth of DVDs. If you have to backup terabytes of data, saving physical space is a big deal--but for a home user, it’s not as important.

There is another advantage to using higher capacity media. If you have a 50GB backup and a 100GB tape, you can complete the backup without switching tapes--but with DVDs you’d have to swap out about 11 DVDs.

Now, before you rush to buy a tape drive, realize that if you only have 50GB of data to backup, you’ll only have to baseline that data once (not every time you back up) and your daily backup will only have to write what has changed since your last backup. So, the baseline may take you a while, but the daily backups will be a breeze.

You can also hook up two DVD drives to your computer, letting the software switch between them automatically, letting you back up more data before you have to switch discs.

Cost per GB
Another important factor is cost per GB. Obviously, the lower the cost per GB of a medium, the less a backup will cost us to make.

DVD-R media has the lowest raw cost per GB. With discs averaging $0.80 per 4.7GB disc (4.2GB of which is useable), the cost per GB is about $0.19/GB.

Sony AIT tapes cost between $0.60 to $1 per GB new, depending on the capacity. You can also find new and used tapes on Ebay. Because of the ruggedness of the Sony AIT tapes, and software verification, used tapes are usually as good as new tapes.

Of course, there are other tape devices available as well, with similar costs per GB.

Tapes cost more and often require expensive drives, but they are more compact and allow larger backups to be completed with less media swapping (or no swapping if you use automated library drives that can contain dozens to hundreds of tapes). For corporate IT systems, tape backup is great, but for home use, it may not be necessary.

It’s common to see capacities on tapes rated as the “compressed” capacity, or for backup software to claim that it can compress files. If you are mainly backing up Power Point presentations and word processing documents, these numbers may be true. In my experience, image files don’t compress well, if at all, with the compression schemes used by backup drives and backup software. Expect the uncompressed capacities to be accurate.

Ruggedness
If your backup media becomes physically damaged, you won't be able to retrieve your files when you need them most. Ideally, whatever media you choose should be able to handle “normal” handling that is necessary to use it in the first place.

The only bad thing I can think of with DVDs is they can scratch from handling, whereas a tape is protected inside a cassette. The lifetime for Sony AIT tapes is about 1000 uses, which is far more than even most corporate users would ever use.

I can speak from my own experience to say that tapes are very reliable and defects or problems are very rare. I do not yet have the same amount of experience with using DVDs for backup.

Longevity.
According to the National Institute of Standards and Technology, a DVD-R should last 100 years. By that point in time, you will have a hard time finding a computer that will be able to read the DVD! Sony AIT are rated for 25 years, which I also think is more than adequate. What you want is for the data to last long enough so you can migrate it to another media type as the old type comes obsolete.

Conclusions
I started this article expecting to demystify using tape backup systems and justify their cost, but I came to some unexpected conclusions. In the last few months we’ve seen a radical drop in the cost of both DVD-R drives and DVDs, along with much faster drives. This has suddenly made DVD a very attractive solution for home users and low-volume backup situations. It also gives us a backup solution at a price point that is more easily justified by most users (who may already have a DVD writer). This means that more people are likely to start backing up properly and regularly.

There are still some situations that call for tape systems, which are purposely made for high reliability in critical backup applications. My years of experience with such systems makes me very comfortable with them--yet every technology gets eclipsed sooner or later.

Before I used a tape backup system, I archived everything to Gold CD-R, and I’m able to consistently access discs burned six years ago, so it’s probably reasonable to expect that if I carefully handle DVD media, I should be able to use them well into the future.

There is no perfect solution, and it’s your responsibility to make sure you have an adequate backup of your data--but given that, I think a 8x DVD-R and some good backup software would serve the average photographer very well.

If you’ve decided on a drive and media type, now you’re ready to talk about backup software and learning how to use it--but that will have to wait for our next installment!

Click to read part one or part two on this topic.