Questions about Time Machine

I've had my Mac since 2009, but just recently upgraded to Mavericks. I did not have my drive backed up so I lost a lot of data because it crashed while upgrading to Mavrericks. I have a new 320GB drive installed now with Mavericks. Some information was retrieved from the old drive, but not everything. I have an external drive 500GB and I am now backing up my drive. Does this back up everything on the drive? Should I always have my external drive connected? What if my external drive runs out of space. I do have some stuff backed up already. I guess if I had backed up everything from my old drive, I wouldn't have to manually input all my stuff. I may have more questions.

Time Machine will backup everything on your internal hard drive.
Be aware that a time machine backup is not bootable, so if ever you need to restore your complete system you will need to install the OS first and then restore from the TM Backup.
Time Machine will also ensure that your backup drive does not run out of space by deleting the oldest backups when needed.
It is always a good idea to have a bootable backup using Carbon Copy Cloner or SuperDuper!

Cheers ... McBie

OK, but should I leave my external drive connected all the time?

If you want Time Machine to back up on schedule then yes the drive needs to be connected for that to happen. Some people choose to leave the external drive unplugged as a means of controlling how often Time Machine runs. There is also third party software to control Time Machine for those who feel hourly backups are too much.

There are a couple of things to keep in mind about Time Machine:

1. Some Macs continue backing up even if the external drive is not connected. These local snapshots take up space on the main drive until the Time machine drive is connected again. About Time Machine local snapshots

2. Time Machine backs up everything unless you tell it otherwise.

3. With recent versions of Time Machine you can backup to a network device.

This article will get you up to speed on the basics. It' s five years old (wow) but the basics of Time Machine haven't changed much.