I added an internal SATA II hard disk which is the exact same size as my main drive (320Gb). I use rsnapshot to create a daily backup and have stored a ghost image on it as well, although it's currently outdated.
I also use a external drive (160Gb) which I use for some data archiving but I also use it to store some backups on it. I'll be on a vacation soon so I just put the most recent backup on the external drive which will be kept safe at another house. In case of fire. Although I should do that more often.
If it's just for backup then I'd say it wouldn't really be necessary to have a extremely big drive. On the other hand, multiple backups won't do any harm.
About the different brands. So far I never had a hard disk from Maxtor fail on me. Seagate did fail multiple times. But that was over 5 years ago and I believe Maxtor is now owned by Seagate. So I guess it doesn't matter anymore :-).
I also use a external drive (160Gb) which I use for some data archiving but I also use it to store some backups on it. I'll be on a vacation soon so I just put the most recent backup on the external drive which will be kept safe at another house. In case of fire. Although I should do that more often.
If it's just for backup then I'd say it wouldn't really be necessary to have a extremely big drive. On the other hand, multiple backups won't do any harm.
About the different brands. So far I never had a hard disk from Maxtor fail on me. Seagate did fail multiple times. But that was over 5 years ago and I believe Maxtor is now owned by Seagate. So I guess it doesn't matter anymore :-).