We were talking about RAID a few days ago and how they are different from backups.
• RAID helps to protect you against hardware failure, the idea is that you can have a disk fail and still continue running, then replace the broken disk and rebuild to give you a protected system. •• Different levels (sorts/types) of RAID. The easiest to understand is RAID-1 where you have 2 (or more) disks that contain identical data, it is sometimes said that the 2 disks are mirrored. •• If you delete/mess-up a file it will be deleted/messed-up on both mirrored disks. RAID does not protect you from fat fingers or programming errors. • Backups - you take a snapshot of your system, prolly daily, and can restore all (or part) of the snapshot - great for getting back the file before you deleted-it/messed-it-up. •• There are different sorts of backup: full (ie all files); incremental (what has changed since the last full backup); other strategies. The reason that I am talking about this is because of the problems at matrix.org. Their RAID system failed, I do not know why or what RAID system they have. This should never happen - but one thing that I have learned with computers is that when someone says that something can never happen: I take that to mean that it only happens rarely. So: they had a RAID failure, all data in the RAID system is lost. BUT: they have backups and after mending the RAID system are restoring from backup. They have somewhere a copy of changes made since the backup and are replaying them. They will end up having lost nothing (or very little); they will have been off-line for a day or so and will have some egg on their faces -- but it could have been much worse. Learning point: Use RAID for must-never-stop systems AND have backups. https://www.theregister.com/2025/09/03/matrixorg_raid_failure/ Sorry if I sound like a preacher, hopefully this will someday save the backside of someone who reads this. -- Alain Williams Linux/GNU Consultant - Mail systems, Web sites, Networking, Programmer, IT Lecturer. +44 (0) 787 668 0256 https://www.phcomp.co.uk/ Parliament Hill Computers. Registration Information: https://www.phcomp.co.uk/Contact.html #include <std_disclaimer.h>
