RAID & Backups
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>
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