Your Image Is Everything
Protection Against Computer Calamities:
A Snapshot of Your Hard Drive
July 28, 2006
A few weeks back, I wrote about the principles of backing up your data ("The way forward: Back up," June 16) and promised I would then tell you in more detail how to do so. But first, let's address the worst-case scenario: You lose everything when your laptop catches fire. (It happens -- trust me.) Then your concern isn't just losing the photos of Timmy's first steps; it's getting your whole life back. If your hard drive dies -- and it will, one day -- you will be looking for a way to restore things to as recent a state as possible. Backing up individual files is important, and something we'll go into later, but the cornerstone of your strategy should be having a backup of your whole computer.
This is why the first step I want to tackle is the disk image: taking a snapshot of all the data on your hard drive and recording that snapshot on a separate device, whether it's another hard drive, or disks such as CD-Rs or DVDs. This isn't about copying files from one place to another, but using software that creates a kind of replica of what's on your hard drive, but compressed into a single file, which can then be restored should something go wrong.
It's not particularly popular among nongeeks, because it can be rather challenging to do, but it makes a lot of sense. For one thing, the prices of hard drives have fallen precipitously. For another, the process has gotten easier and isn't as time-consuming as you might think: When I took a snapshot of my 40-gigabyte hard drive, it took about half an hour. The payoff is obvious: Even if your hard drive crashes, or weird stuff starts happening because of a virus, you can restore the backup image and you'll be back in action in a few hours.
So how does one do this? Well, first you need the hardware. You need your computer, with either a CD burner or DVD burner attached to it. Or, even better in my view, a hard drive connected directly to your computer. (If it's a desktop computer or one of those laptops that have space for two hard drives, it can be inside. If not, the hard drive can be an external one.) Then you need the software. For Mac users, Carbon Copy Cloner (
www.bombich.com/software/ccc.html; free, but donations welcome) has a good reputation. The most popular Windows program is Norton Ghost ($70 from Symantec Corp.), but I had problems launching it, so much so that I ditched it. Another promising-looking program, FarStone Technology Inc.'s RestoreIT ($60), also failed at the first hurdle -- installation problems this time. One that did work for me was Acronis Inc.'s True Image Home ($50), which has an acceptable interface and one of those wizard things that take you by the hand and lead you through the process. This makes it all quite simple: Select "backup" and then just answer the questions.
These programs will then create what is called a disk image on your other hard drive or the CD/DVD. The image is one file, large because it's a snapshot of all your data, but quite a bit smaller than the data it is capturing because it's compressed. It will probably still be too big for any one CD to hold, and it may be too big for a DVD -- in which case the software slices the image file into smaller bites that can fit on each disk.
Now you have a backup of your entire hard drive. Should something go wrong with the original, you can restore it to the state it was in when you made the image. But you need to take one more step first, so you can restore the backed-up version even if your main hard drive is no longer functioning: Create what is called a boot-up disk. This is (usually) a CD-ROM that, if it's inside your CD-ROM drive when you turn your computer on, will bypass your computer's hard drive and load the basic operating system files that make it run. This backup CD is your spare key to the computer. Keep both the disk image and the boot-up disk in a safe place.
Now, it's important to note what these disk images are and what they aren't. A disk image will save all your files -- including your all-important program files -- from any disaster that may befall your hard drive. You're not going to be able to look inside the image file to retrieve individual files, should that be all you're looking for. It's all or nothing: You either restore the whole of your hard drive or nothing. They're also only as good as the time you made them: If you made a disk image six months ago, it isn't going to know what's been going on in your computer since then. Finally, a disk image isn't infallible. David Weinberger, a fellow at Harvard Berkman Center, a Harvard Law School project that researches the relationship between the Internet and society, uses them, but says they have sometimes failed on him. The reason can be anything from a faulty image file to flaky storage media. "Sometimes you can get the data back and sometimes you can't," he says.
That's why you need to follow the ABCs of disk imaging: A) Do it as often as you can and, if you have the space and time, make two copies each time. B) If you're backing up to a hard drive and you can afford the space, don't overwrite previous images; if one of them fails, you'll still have another. If you're backing up to a CD or DVD this shouldn't be an issue; just make sure you include dates on the label. And, most importantly: C) Don't rely on any one system. A disk image is just your first line of defense.
That's why I need to write some more columns about this.
用映像文件备份整个硬盘
几周前，我曾写过一篇关于备份数据的文章，并且当时承诺进一步讲讲备份的细节。但是，假如发生了最糟糕的情况──你的笔记本电脑著火了，导致一切数据丢失──这时候该怎么办？相信我，这种情况确实可能发生。如果发生这种情况，要做的恐怕就不仅仅是如何找回宝贝初学走路时候的照片这样简单了；你肯定希望把电脑中存储的所有数据都找回来。如果你的硬盘“罢工”了（这种情况迟早会发生），你一定希望修复硬盘上面的数据，而且最好能恢复成最近的状态。对个别文件进行备份固然重要，我们也会在后期的文章中讨论这一点，但今天我要谈的是最基本的备份策略──对整个电脑进行备份。
第一步就是创建硬盘映像文件，把硬盘上存储的所有数据制作成一个映像文件，然后把映像文件刻录在其他驱动器上，另一块硬盘、普通光盘、DVD光盘都可以。这并不是简单地把数据从一个地方复制到另一个地方，而是用软件复制硬盘资料，然后压缩成一个文件。这个映像文件在系统出现故障时可以帮你恢复硬盘上的数据。
对电脑不大精通的读者可能并不热衷于此，因为制作映像文件具有一定的难度，但是映像文件可以派上大用场。首先，硬盘价格已经直线下滑，另外，制作映像文件的过程现在容易多了，也不像想象中的那样费时。我为我的40G硬盘制作映像文件大概花了半个小时的时间。回报是巨大的，即使硬盘崩溃了，或者因为中毒出现了一些稀奇古怪的东西，你可以通过映像文件使系统在几个小时后恢复如常。
那么具体是怎么操作的呢？首先，你先得有一个用于存储的硬件。你的电脑应该配有一个光驱刻录机或者DVD刻录机。在我看来，你如果有一个直接连接你电脑的硬盘就更好了。如果你的电脑是台式机或者可以容纳两个硬盘的笔记本电脑，那么用于备份的硬盘是否内置就无所谓了，否则，我建议你使用外置硬盘。接下来就是软件的事情了。苹果机的用户可以使用Carbon Copy Cloner这个有著良好声誉的软件（下载网址是
www.bombich.com/software/ccc.html，当然也欢迎你付费）。对于Windows用户而言，最流行的备份软件当属Norton Ghost（花70美元可以从赛门铁克公司(Symantec Corp.)买到）。但我在安装该软件时遇到了不小的麻烦，以至于最后只能放弃。另一款看上去不错的软件是FarStone Technology Inc.出品的RestoreIT（花60美元可买到），可是我还是在安装时出现了问题。真正起作用的是Acronis Inc.开发的True Image Home（售价为50美元）。该软件界面友好、安装向导手把手地指引你进行安装，直到你完成安装为止。操作起来也很简单：选择“备份”选项，然后回答一些问题就大功告成了。
该软件会在你的其他硬盘上或者CD/DVD上创建一个映像文件。映像文件很大，因为它记录了所有数据的信息，但由于经过了压缩，它比在硬盘上实际所占用的空间小了一些。也许映像文件的大小会超过普通光盘、甚至DVD光盘的存储空间。如果这样的话，该软件可以对原映像文件进行“瘦身”，把原文件切割成普通光盘或DVD光盘可以装得下的文件。
因为是把整个硬盘给备份了，一旦电脑运转异常，你就可以调出映像文件，然后把硬盘恢复至上次备份时的状态。但在此之前你还应做一步：创建一个启动光盘。这样即使主板坏了，你也可以调用映像文件。有了启动光盘，电脑就无需借助硬盘而是直接从光盘启动了。因此，备份光盘对于你的电脑来说就像是一把备份钥匙。切记，把映像文件和启动光盘放在一个安全的地方。
需要指出的是，映像文件可以把你所有的文件从灾难中拯救出来，但是你无法从中只调用个别的文件，其结果也就是要么恢复整个硬盘，要么什么都恢复不了。另外，映像文件只能保存你最近一次制作它们时的信息，也就是说，如果你制作映像文件是在6个月前的事，那么在这6个月期间，所有的信息变化都无法记载下来。还有，映像文件也有失灵的时候。Harvard Berkman Center的研究人员David Weinberger就发现：映像文件时灵时不灵，原因可能在于映像文件有缺陷，或者存储介质运行不稳定等。
简而言之：在制作映像文件时应遵循以下步骤：一、在你有存储空间、有时间的时候尽量多生成映像文件；二、如果你用硬盘备份，只要有足够的存储空间，就别抹去以前的映像文件。因为，如果其中一个映像文件失灵了，那么你还有其他文件可供利用。如果你把映像文件保存在了光盘里面，就没这方面的问题了，但是记住：在标签上写下每次备份时的时间；三、这是最重要的，不要只依赖于一种系统。映像文件只是你的第一道防线。
Jeremy Wagstaff
