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I have a large ext4 disc of 15qty x 10TB hdds in an Areca 1880ix-24 RAID6 array. I know RAID does not equal backup, but the contents of this 120TB+ drive are static media files, which, if necessary, could be very slowly and painfully downloaded again.

The server is running Ubuntu 18.04.
I'm trying to look forward to the possible situation where some sort of corruption occurs to the ext4 partition and/or directory, and I'm not able to recover, despite for instance, the multiple magic values sprinkled across the disk.
Assuming that almost none of the data changes on a month to month basis, and assuming that the corruption is isolated to the ext4 allocation tables and/or whatever critical underlying structural metadata exists, I'd like to take the occasional snapshot of said structure to use if needed in some future recovery.
I'm a long-time Windows guy but I don't know much about ext4, but I do know that there could well be some future problem that results in the inability to mount or access the countless extent of files across more than 100TB of data.
Ignoring for a moment that there are different ways to store said data that reduce this sort of risk, there remains the possibility of corruption of critical data that doesn't affect the actual files themselves, but renders them inaccessible.
I'd like to minimize that possible impact. Is there a utility, script, or SOP that I can employ to help reduce this impact?

Melebius
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Doug Parsons
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    Ubuntu 18.10 is EOL (https://fridge.ubuntu.com/2019/07/19/ubuntu-18-10-cosmic-cuttlefish-end-of-life-reached-on-july-18-2019/) and thus off-topic on this site (https://askubuntu.com/help/on-topic) unless questions are specific to moving to a supported release of Ubuntu. Use a LTS release if you don't like release-upgrading every 6-9 months; and note 19.04 will soon be EOL thus making upgrading your system harder when it does reach EOL. – guiverc Nov 12 '19 at 04:20
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    Sorry, I made a typo. It's running 18.04.3 LTS. Here's my version details: root@sophie:/# uname -a Linux sophie 4.15.0-65-generic #74-Ubuntu SMP Tue Sep 17 17:06:04 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux root@sophie:/# lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 18.04.3 LTS Release: 18.04 Codename: bionic – Doug Parsons Nov 13 '19 at 05:10
  • @DougParsons Have you been satisfied with my answer? If I could solve your problem, it would be nice if you accepted my answer (✓). In the opposite case, please clarify your needs using [edit]ing or comments. See also What should I do when someone answers my question?, How does accepting an answer work? – Melebius Nov 21 '19 at 08:07

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In Linux (but also in Windows), you can divide your disk into multiple partitions and backup just some partitions.

Create a separate partition for your static media files and keep the system in another partition. The system partition could take 10–20 GB in such a setup which would be quite easy to backup.

If your media files belong to user contents, consider creating a separate home partition, see How to create a separate home partition after installing Ubuntu under single / partition. If they are placed in another location (e.g. /var), you can create a new mount point similarly.

Melebius
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