This document outlines the levels of data protection different technologies you may consider or use often. It may be used as a basis for understanding your acceptable level of risk and to assist you in deciding if you need to backup your data. None of the technologies listed here are considered a backup platform.
SSD Disk - SSD's or Solid State Drives, are more reliable than spinning disks, but do catastrophically fail as well.
RAID - While there are many different types of RAID it primarily provides performance and protection from single disk failures.
ZFS - ZFS combines multiple disks without using a RAID controller to provide performance and protection. Additionally it can, and should be configured, to provide incremental snapshots to provide additional data protection. ZFS with snapshots is what is below.
Redundant servers - 2 servers or NAS's (Network Attached Storage) providing the same service with a synchronized copy of the same data. This provides higher availability but not data protection. The servers will dutifully synchronize most common data destruction events to the other one.
This table shows common data loss scenarios and if a given technology will protect your data.
|Single HD||RAID||ZFS||Redundant Servers||Backups|
|Individual disk hardware failure||Yes||Yes||Yes||Yes|
|Multiple disk hardware failure||Maybe||Maybe||Yes||Yes|
|Total HW Failure||Yes||Yes|
|Disaster - Fire / Flood||Maybe||Yes|
|Users deleting files||Maybe*||Yes*|
|System admin mistakes||Yes*|
|Malicious users or code||Maybe*||Yes*|
|Malicious system admins||Yes*|
* Retention period is important. Typical ZFS retention periods are 2-10 days. Typical backup retention periods are 60+ days.
"Backups" are a software agent based system where changes to your data is automatically copied on a given interval to a remote backup solution. Ideally this interval would be 24 hours or less.