You’ve been through this before. A smart-aleck technology columnist tells you to back up your computer files or else. Sure enough, you choose “or else,” because making spare copies of your files is too much bother.

You don’t want to spend $100 or more on an external hard drive or figure out how to install the automatic backup software. Besides, if your house is robbed or burned down, there goes your computer and your precious backup, too.

Unless your backed-up data wasn’t home when disaster struck.

These days you can copy your files over the Internet, and store them at a high-security data center, with help from an online data backup service.

Not many consumers presently use online backup — only about 1.5 percent, according to a survey taken last year by research firm IDC Corp. in Framingham, Mass. But lots of companies offer online storage for small amounts of data, often at no charge. Two firms promise to store every file you’ve got for as little as $50 a year.

Both of them have a Massachusetts connection. Last year, EMC Corp. in Hopkinton purchased Berkeley Data Systems, a Utah company that offers Mozy, an online backup service for consumers and businesses. Meanwhile, in Boston, a homegrown outfit called Carbonite has offered online backup since 2006. Based on our tests, you can’t go wrong with either Mozy or Carbonite, but we’d give Carbonite the edge, thanks to its brain-dead simplicity and slightly lower price.

Carbonite costs $49.95 a year or $89.95 for two years of service. Mozy’s consumer service, MozyHome, charges $4.95 a month, or $59.40 a year — but you get a free month’s service if you pay for a year in advance. In exchange, both companies say you can back up as much data as you wish. Mozy also offers a free service that’s…