4 ms·

If the only instance of a thing is on your "back-up" drive then it isn't a back-up.

by alexkus 13y ago

mikeash 13y ago
Data that isn't backed up (as in a second copy) doesn't really exist. Likewise: data that isn't backed up off site isn't really backed up.
- alexkus 13y ago
  Untested backups don't exist either. There are several horror stories of people going to their offsite tape backups to restore some lost data only to find that their backups didn't work due to a malfunctioning tape drive. Other stories about encrypted backups where the decryption key is lost (backup data is encrypted with a randomly chosen "session" key, session key is encrypted using a public key, no-one could find the appropriate private key to decrypt the session key. etc...
  - tehwalrus 13y ago
    I heard about a private school that backed up its fee database (MS Access) to a USB stick every night - in fact what the accountant was doing was backing up the desktop shortcut to the database. In the event of the failure that revealed the problem, they lost about 7 months worth of data (which was the time since the computer had last been connected to the network, and had synced via Active Directory, or whatever they call it.)
- brazzy 13y ago
  > Data that isn't backed up (as in a second copy) doesn't really exist. An IMO more realistic statement: Data that is not backed up is implicitly classified as "nice to have" - in many cases a perfectly rational choice, if done consciously. > Likewise: data that isn't backed up off site isn't really backed up. You may as well argue that no data is ever "really" backed up because there is always the possibility of simultaneous failure. It's always a choice of how much risk you're willing to accept vs. how much money and effort it would cost to reduce it further.
  - mikeash 13y ago
    Yep. 1 copy of data is not enough, because it can be lost. Now, assuming that N copies of data is not enough, it's easy to see that N+1 copies is also not enough, because that extra copy can be lost, thus reducing to N copies, which is not enough. This proves by induction that no matter how many backups you have, it's not enough.
TheLoneWolfling 13y ago
Agreed. I currently have two external drives: an archive drive and a backup drive: both 2TB. (Most things on the backup drive are compressed and deduped, which is why I can fit everything.)

If the only instance of a thing is on your "back-up" drive then it isn't a back-up.

by alexkus 13y ago

If the only instance of a thing is on your "back-up" drive then it isn't a back-up.

Data that isn't backed up (as in a second copy) doesn't really exist. Likewise: data that isn't backed up off site isn't really backed up.

alexkus 13y ago
Untested backups don't exist either. There are several horror stories of people going to their offsite tape backups to restore some lost data only to find that their backups didn't work due to a malfunctioning tape drive. Other stories about encrypted backups where the decryption key is lost (backup data is encrypted with a randomly chosen "session" key, session key is encrypted using a public key, no-one could find the appropriate private key to decrypt the session key. etc...
- tehwalrus 13y ago
  I heard about a private school that backed up its fee database (MS Access) to a USB stick every night - in fact what the accountant was doing was backing up the desktop shortcut to the database. In the event of the failure that revealed the problem, they lost about 7 months worth of data (which was the time since the computer had last been connected to the network, and had synced via Active Directory, or whatever they call it.)
brazzy 13y ago
> Data that isn't backed up (as in a second copy) doesn't really exist. An IMO more realistic statement: Data that is not backed up is implicitly classified as "nice to have" - in many cases a perfectly rational choice, if done consciously. > Likewise: data that isn't backed up off site isn't really backed up. You may as well argue that no data is ever "really" backed up because there is always the possibility of simultaneous failure. It's always a choice of how much risk you're willing to accept vs. how much money and effort it would cost to reduce it further.
- mikeash 13y ago
  Yep. 1 copy of data is not enough, because it can be lost. Now, assuming that N copies of data is not enough, it's easy to see that N+1 copies is also not enough, because that extra copy can be lost, thus reducing to N copies, which is not enough. This proves by induction that no matter how many backups you have, it's not enough.

TheLoneWolfling 13y ago

Agreed. I currently have two external drives: an archive drive and a backup drive: both 2TB. (Most things on the backup drive are compressed and deduped, which is why I can fit everything.)