Great writing. however a question for geeks. what is wrong with using RAID0 for performance along with external backup/deduplication solution like borg backup/duplicati etc... ?
As long as your choice of RAID0 is an informed one (i.e., you are fully aware of the risks and failure modes as well as the benefits -- and it sounds like you are), there's absolutely nothing wrong with using it.
There are three drawbacks to the setup you describe:
- If a drive fails, the system is offline until you restore from backup. Fine for personal use, but not okay if customers are paying you for a service.
- If a drive fails, any changes since the last backup are lost. Fine for long-term archival, not so great for a bank ledger.
- No capability to detect data corruption. RAID with parity can run a scrub to find and repair bit rot. If data is corrupted on your RAID 0, you probably won't notice, and you'll back up the corrupted. If your filesystem has checksums you will be able to detect the corruption but not repair it. Your filesystem probably doesn't have checksums.
If you frequently run I/O intensive workloads, the extra performance might be worth the tradeoffs. If you're looking for your PC to feel slightly faster it seems foolish.
- I've got 1 HDD failure on RAID10 4 x 10TB HDDs, I had to take the system down to do RAID10 rebuild. because running server with huge I/O slowdown the rebuild and I had my fears of second HDD failure. (I had to take the system down anyway).
RAID didn't help in my usage scenario.
- I guess deduplication fixes this already.
- Any advice on ways fixing this and preserving my RAID0 usage scenario?
Broadly speaking, you have two options. One is, make the server faster so that it can keep operating during a rebuild. You could do this by adding more drives. The other option is, add a second server to handle the load while you fix the first.
It depends only on whether you can afford to lose the data.
I'm using two SATA SSDs in md RAID0 for VMs on my desktop (where each VM gets its own LV). Dangerous thing, but if one of them fails, nothing happens, I will shrug and reinstall.
You can take as an example the Recovery Point Objective and Recovery Time Objective terms used on disaster recovery. Depending on: a) how often you do backups, b) how many data are you backing up, and c) how fast are your network and transfer medium, you can calculate how much data you may lose in case of failure and how much time you'll use on recovery.
