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Comment by PhilipRoman | Hacker News Reader

To be honest I never understood the purpose of RAID for personal use cases. RAID is not a backup, so you need frequent, incremental backups anyway. It only makes sense for things where you need that 99.99% uptime. OK, maybe if you're hosting a service that many people depend on then I could see it (although I suspect downtime would still be dominated by other causes) but then I go over to r/DataHoarder and I see people using RAID for their media vaults which just blows my mind.

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RAID is not backup, but in some circumstances it's better than a backup. If you don't have RAID and your disk dies you need to replace it ASAP and you've lost all changes since your last backup. If you have RAID you just replace the disk and suffer 0 data loss.

That being said, the reason why I'm afraid of not using RAID is data integrity. What happens when the single HDD/SSD in your system is near its end of life? Can it be trusted to fail cleanly or might it return corrupted data (which then propagates to your backup)? I don't know and I'd be happy to be convinced that it's never an issue nowadays. But I do know that with a btrfs or zfs RAID and the checksuming done by these file systems you don't have to trust the specific consumer-grade disk in some random laptop, but instead can rely on data integrity being ensured by the FS.

You should not propagate changes to your backup in a way that overwrites previous versions. Otherwise a ransomware attack will also destroy your backup. Your server should be allowed to only append the data for new versions without deleting old versions.

Also, if you're paranoid avout drive behavior, run ZFS. It will detect such problems and surface it at the OS level (ref "Zebras All The Way Down" by Bryan Cantrill)

Convenience. If you lose a disk you can just replace it and don't need to reinstall/restore the backup.

Also, because it's fun and probably many self-hosters had racked servers and plugged disks in noisy, cold big chambers and they want to live again the fun part of that.

RAID isn’t backup - but in my years running computers at my house I’ve been lucky enough to lose zero machines to theft, water damage, fire, etc. but I have had many hard drives fail.

Way more convenient to just swap out a drive then to swap out a drive and restore from backup.

Interesting, I've had the exact opposite experience. My oldest HDD from 2007 is still going strong. Haven't had even a single micro SD card fail in a RPI. I built some fancy backup infrastructure for myself based on a sharded hash addressed database but so far have only used the backups to recover from "Layer 8" issues :)

I had a look at my notes and so far the only unexpected downtime has been due to 1x CMOS battery running out after true power off, 1x VPS provider randomly powering off my reverse proxy, 2x me screwing around with link bonding (connections always started to fail a few hours later, in middle of night).

It's incredibly valuable. It makes redundancy really affordable.

This means nothing until the need to replace one drive arises, then it's not an if..

No downtime with raid 5, you can swap out one drive as needed while the rest runs just fine.

I like snapraid for media drives. As long as it’s something without lots of deletes and changes, I bet more space and can use mixed drives and get a bit of a backup too since it’s a manual sync to create or update the “parity”. And the added advantage that any drive taken out or they dies you still can read any if the content on the other drives at any time.

I'll check out snapraid, thanks.

The challenge is a "bit of a backup" is risky. There's no back up if it's only a single copy of something, or even a single copy of something.

3-2-1 backups are really in time teach everyone the lesson that you don't buy storage, you buy backups, some that are more quickly accessible than others.

The cost of "maximizing" space with the drives I have, for example, is relatively trivial and simpler, its in the hundreds of dollars now instead of thousands. The upside is huge.

Solely trusting third party services is risky, and locally holding your data can be relatively managed well.

Sure. I am just using it for my media server which I could “re-acquire” if I really needed too.

What I meant by “bit of backup” was you could actually restore files that were deleted since the last sync since it’s not always live like RAID and requires scheduled syncs to update the parity info. It’s a compromise I make as a home user for my media server.

i use mirror raid on my desktop. the risk of a disk dying is just to high. i even made sure to buy disks from two different vendors to reduce the chance of them dying at the same time. for the laptop i run syncthing to keep the data in sync with the desktop and a remote server. if the laptop dies i'll only be a few minutes out. when travelling i sync to a USB drive frequently.

for the same reason i don't buy laptops with soldered SSD. if the laptop dies, chances are the SSD is still ok, and i can recover it easily.

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