How would you implement a data backup strategy?

Data backup strategy typically includes several key steps:

1. Identifying critical data — determining which data needs to be preserved.
2. Choosing the type of backup:
   • Full — copying the entire database.
   • Incremental — copying only changes since the last backup.
   • Differential — copying changes since the last full backup.
3. Backup frequency — depends on recovery requirements and data volume.
4. Storing backups — preferably using different physical media and geographic locations to protect against loss.
5. Automating the process — using scripts or specialized tools (e.g., rsync, Bacula, Veeam).
6. Recovery testing — regularly verifying that backups can be successfully restored.

Example of a simple script for incremental backup on Linux using rsync:

#!/bin/bash
SOURCE_DIR="/data"
BACKUP_DIR="/backup/$(date +%Y-%m-%d)"

mkdir -p "$BACKUP_DIR"
rsync -av --delete --link-dest=/backup/last_backup "$SOURCE_DIR/" "$BACKUP_DIR/"
rm -f /backup/last_backup
ln -s "$BACKUP_DIR" /backup/last_backup

This script creates an incremental backup with hard links to the previous one, saving space.