Disk Partitions

What is a partition and why would I want one?

A partition is a way to divide up a hard drive and have your Operating System (Mac or Windows) “think” it is 2 or more drives. The main reason to do this is organizational. There are some theoretical performance gains, but these are probably not noticeable.

You have 2 types of information on your computer. One is the system and the programs you install. These do not change drastically most of the time and do not need daily updating. If you did have to restore to a previous time, you could run updates fairly easily to bring it back to the current state. You would want to update a backup after adding or removing a significant program, especially after adding a program that is hard to install or one that you tweaked a lot.

Your other data is your personal documents, pictures, music, emails, etc. You are continually adding to and deleting from this collection, and changing the content in some of it. This stuff needs to be backed up frequently, perhaps even several times a day if you are very active and it is important.

The 2 types of data have different, conflicting needs. The system/program data is best done by a disk image, a verbatim copy of the drive. This makes a large set of files you will need to store somewhere. It is also a more involved process. If you have all of your changeable personal data with the system, the image will take much longer to make and need more space to store. The image of all those personal files will be useless after a day or so. You will need a separate backup of them each day, anyway.

Your changeable personal data is best backed up with a copy program that will check to see what is new or changed and copy that to a backup location. These can run automatically or are very easy to initiate. They run very quickly. If you copy all of the system and program files, the job again takes much longer and needs more storage space. It might be handy to have those copies, but if you need to restore from a drive disaster or a munged system, you can’t just copy the files to a new drive and boot from it. You need the disk image or install disks for that. So those copies of system files really don’t do much for you.

With 2 partitions, you put the system and programs on one and the changeable data on the other. You can then optimize the backup of each partition. If your system becomes unbootable because of software issues, you can work on the system partition – even restore it if needed – without affecting your data. HOWEVER: you really don’t have 2 hard drives, just the appearance of that. So if the hard drive actually physically breaks, both partitions are lost. Your data backups and your image should be on a separate hard drive removed from your computer, or on DVDs.

If you don’t have a lot of changeable data, the inefficiency of imaging it is not that bad and you may not really need the partitions. You do still need the 2 types of backup, an image for the system and frequent file copies for your personal data. How much is “not a lot”? Probably about a gigabyte of files.

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