Time Machine is a great feature of OS X that has been around since Leopard and it saves copies of your files at regular intervals to a backup disk. It even does so while you are working on other things. It is like an insurance policy and you hope that you will never need to use it, but if you do, you'll be glad you have it.
One slightly irritating feature of Time Machine is that it can sometimes take a long time to finish its backup job. This happens the first time that you use it of course, because every file on the computer must be copied to the backup disk.
It also occurs if Time Machine hasn't been running for some time, which can happen when you are out with a laptop for a week or even just several days and haven't plugged in to the external hard disk backup drive for a while. The more files that have changed since you last backed up, the longer the backup job will take when you plug in.
You can't speed up the rate at which data is written during a backup, but you can reduce the time taken for the whole job by instructing Time Machine not to back up certain files. Of course, you wan't be able to restore any files that are not backed up, but some just don't need to be backed up.
What doesn't need backing up? Well, how about files in the Downloads folder? They can probably be downloaded again if necessary. You might also have files that you have archived and backed up elsewhere, such as Dropbox. If you use online storage like Dropbox and others then your files are online and you don't need Time Machine to back them up. You can save several gigabytes by adding these files and folders to Time Machine's exceptions list. They won't be backed up and the job will be finished more quickly.
Click the Apple menu in the top-left corner of the screen and select System Preferences from the menu that drops down. Click Time Machine in the System section and then click the Options button. Click the Plus button and then select the files or folders to exclude. You can add as many items as you want to the list. Click Done when you have added them all and close the Preferences window.
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