Think like a pessimist, hope like an optimist
The amount of money to budget for backup costs should equal how much it cost to originally create the data (man hours, customer interaction, equipment). If the data can not be reconstructed, then what is the cost of loss? Most businesses are built on information. Backup is about that information being accessible.
If someone else is in charge of data you need, then you will lose access to it
through their incompetence, politics, miscommunication
solution -> If you need the data, then you need control of the data.
If you have three backups, then
the source machine will crash
the first backup will be corrupt
the second backup won't actually have been copying
the third backup will be lost
solution -> use md5 sums, verify that the backup is valid by testing it, and never rely backups to work
if you have all your backups on-site, then Godzilla* will attack
* Godzilla = fire, bomb, anthrax, theft, nuclear attack, chemical/biological attack
solution -> copies should be stored off-site
if you have backup, it will be stolen/lost
solution -> use encryption
if n technicians know how to access and restore from backup, then they will all be on vacation, sick, or hit by bus
solution -> if you need data, then you need to both have access AND know how to restore
RAID is NOT backup
rm -rf / * affects all the drives in the RAID stack
if doing nightly backups to an external disk
"cp -r" (recursive) is not the same as "cp -r -u" (update) is not the same as "rsync -av"
use rolling backups
if all backup is on one media, then that media type will stop being made in less then 6 months
solution -> diversify your storage media types
Corollary: if your backups can only be read by one software or OS, that OS/software will be extinct
solution -> opensource virtualization software (virtualbox) of the OS with software for reading the backed up data
your storage environment control system will fail
heat, humidity, sunlight
when you restore a backup, it will be under time constraint
solution -> practice restoring
you need something to backup to
this is part of disaster recovery: a backup media is useless without something to restore it to.
solution -> redundant, off-site servers that can be accessed. Off-site laptops available for use by workers in the event of primary site failure
In conclusion, your solution needs to address these concerns.