Never

I still have drawings I made in MS Paint on Windows 95 when it had just come out, my first text document, and the first report I ever typed in grade school.

Btrfs snapshots of the root volume in RAID1 configuration with 8 hourly, 7 daily, 3 weekly, and automated rsync backups to NAS, with primary and secondary offsite, physically disconnected backups stored in sealed, airtight, and waterproof containers at two different banks prepaid storage and with advanced directive in the event of my demise.

Bit of a hobby really. I acknowledge it’s completely unnecessary. I don’t like to lose data.

My PC: Every day and when it is online
My drives the backups go to: Once a week.

As others have said, with an incremental filesystem level mechanism, the backup process won’t be too taxing for the CPU. I have ZFS set up which makes this easy and I make hourly snapshots using sanoid which also get sent to another mirrored pair of connected drives using syncoid. Then, once a day, I upload encrypted daily snapshots to a bucket in the cloud using restic. Sounds complicated, but actually sanoid/syncoid and restic do all the heavy lifting. All I did is automate their schedules using systemd timers and some scripts to backup the right directories.

Daily, usually keeping only the last week or so

There should be a whitepaper you can reference based on sales scenario. As others have said hourly, daily, weekly snapshots are not backups, unless you also have a btrfs or zfs send that IS backing up the snapshots to another remote device

Whenever I’ve gone too far forwards

IMO set up a good incremental backup system with deduplication and then back up everything at least once a day as a baseline. Anything that’s especially valuable can be backed up more frequently, but the price/effort of backing up at least once a day should become trivial if everything is set up correctly.

If you feel like hourly snapshots would be worth it, but too resource-intensive, then maybe replacing them with local snapshots of the file system (which are basically free, if your OS/filesystem supports them) might be reasonable. Those obviously don’t protect against hardware failure, but help against accidental deletion.

When you use deduplication on the backup side you can do backups every minute without needing much storage. When the backup programm looks at the filesystem to determine which file has changed, the CPU only need to process the changed files.

For my personal devices i do daily backups. There is not enough change every day.

I have autocron jobs that sync various server directories to a daily backup (on the same server), then sync that backup once a week to the weekly backup, and once a month take a tarball snapshot of the weekly backup.

Every once in a while I plug in a HDD on USB and take a Borg backup of the monthly dir. Borg does compression and deduplication (and encryption if you want to). I should be doing this also once a week but sometimes I’m lazy and leave a few weeks between them.

Snapahots are not backups!

Snapshots are near instand in ZFS or BTRFS. Also they do not consome much CPU to make them.

Backups are not stored in the same device. What i use to make backups is a combination of borg and urbackup.

It depends what I’m backing up and where it’s backing up to.

I do local/lan backups at a much higher rate because there’s more bandwidth to spare and effectively free storage. So for those as often as every 10 mins if there are changes to back up.

For less critical things and/or cloud backups I have a less frequent schedule as losing more time on those is less critical and it costs more to store on the cloud.

I use Kopia for backups on all my servers and desktop/laptop.

I’ve been very happy with it, it’s FOSS and it saved my ass when Windows Update corrupted my bitlocker disk and I lost everything. That was also the last straw that put me on Linux full-time.

Like you said, “it depends” 😁

I have a huge datablob that I mirror off-site once monthly. I have a few services that provides things for my family, I take a backup of them nightly (and run a “backup-restoration” scenario every six months). For my desktop, none at all - but I have my most critical data synched / documented so they can be restored to a functional state.

stroj task runs daily the initial sync took forever tho because I only have 5MB UP connection

• Personal and business are extremely different. In personal, you backup to defend against your own screwups, ransomware and hardware failure. You are much more likely to predict what is changing most and what is most important so it’s easier to know exactly what needs hourly backups and what needs monthly backups. In business you protect against everything in personal + other people’s screwups and malicious users.
• If you had to setup backups for business without any further details: 7 daily, 4 weekly, 12 monthly (or as many as you can). You really should discuss this with the affected people though.
• If you had to setup backups for personal (and not more than a few users): 7 daily, 1 monthly, 1 yearly.
• Keep as much as you can handle if you already paid for backups (on-site hardware and fixed cost remote backups). No point having several terabytes of free backup space but this will be more wear on the hardware.
• How much time are you willing to lose? If you lost 1 hour of game saves or the office’s work and therefore 1 hour of labour for you or the whole office would it be OK? The “whole office” part is quite unlikely especially if you set up permissions to reduce the amount of damage people can do. It’s most likely to be 1 file or folder.
• You generally don’t need to keep hourly snapshots for more than a couple days since if it’s important enough to need the last hours copy, it will probably be noticed within 2 days. Hourly snapshots can also be very expensive.
• You almost always want daily snapshots for a week. If you can hold them for longer, then do it since they are useful to restoring screwups that went unnoticed for a while and are very useful for auditing. However, keeping a lot of daily snapshots in a high-churn environment gets expensive quickly especially when backing up Windows VMs.
• Weekly and monthly snapshots largely cover auditing and malicious users where something was deleted or changed and nobody noticed for a long time. Prioritise keeping daily snapshots over weekly snapshots, and weekly snapshots over monthly snapshots.
• Yearly snapshots are more for archival and restoring that folder which nobody touched forever and was deleted to save space.
• The numbers above assume a backup system which keeps anything older than 1 month in full and maybe even a week in full (a total duplicate). This is generally done in case of corruption. Keeping daily snapshots for 1 year as increments is very cheap but you risk losing everything due to bitrot. If you are depending on incrementals for long periods of time, you need regular scrubs and redundancy.
• When referring to snapshots I am referring to snapshots stored on the backup storage, not production. Snapshots on the same storage as your production are only useful for non-hardware issues and some ransomware issues. You snapshots must exist on a seperate server and storage. Your snapshots must also be replicated off-site minus hourly snapshots unless you absolutely cannot afford to lose the last hour (billing/transaction details).