Selfhosted

RAID isn't backup, or even redundancy, it's for creating large storage pools. It's at the mercy of the controller and all the hardware. In fact, the more disks you have, the more likely you are to be impacted by a failure.

In a typical RAID 5, if one drive fails, the entire array is at risk until the drive can be replaced, and resilvered. During resilvering (rebuilding the drive with all the data it should have, parity, etc), the entire array is at even more risk because of the load on the other disks.

With dual parity and hot spare (less data storage total), you get a little more security since the parity is doubled and the hot spare will be automatically resilvered if a drive fails, but that's not without similar risks during that process.

You still need backup.

Here's a real-world example of RAID risks. I have a 5-drive NAS with 5 1TB drives, which gives me roughly 4TB of usable space (1TB parity). It runs software RAID using ZFS (a highly resilient file system, that can build arrays using varying disk sizes, and has some self-healing capability). I've had a drive go bad, replacing took 30 hours to rebuild. During that time, the entire array is "degraded", meaning no parity protecting the data because it's currently rebuilding the parity. If another drive were to have failed during this read/write intensive period, I would have lost ALL the data.

To protect against this, I have 2 other large drives which this data is replicated to. And then I use a cloud storage for backup (storj.io).

This is a modified version of the 3-2-1 method that works for my risk assessment.

Without offsite backup, you're always at risk of local issues - fire, flood, etc. Or even just a massive power spike (though that's not much of a risk, especially if you use a UPS).

I'm actually building a second NAS to have easier local redundancy, and because I have a bunch of drives sitting around. With TrueNAS or Unraid, it's pretty easy to repurpose old hardware. Though power is always a concern, so I'm looking for an inexpensive motherboard that has low power draw at idle.

Not if you get a laptop that supports battery charge limiting. Like a Thinkpad.

Never had this happen, and I've carried laptops since the mid 90's, and they've always been plugged in most of the time.

Get to office, plug on, get home, plug in and sit overnight in the charger with no use.

I've seen a few expanded batteries, but that's across the hundreds of laptops in my support circle. It's very rare.

Every laptop I've had in the last 5 years has battery protection built in anyway. I'm running 2 laptops from 2019 that have it.

Though you do make a good point, something to figure out if your laptop does this. And to keep an eye on the batteries anyway (like check battery health quarterly), and replace if it gets down significantly (I replace mine at 70% health).

Spicy Pillow!

USB isn't good for RAID, it's unstable.

Do you currently have more than 8 or 12TB of data? Because you can buy drives that size today, no need for RAID under those capacities.

I recently purchased an 8TB drive for ~$100 on Amazon. Yes, it's used, but comes with a 3 year warranty. I'm fine with that warranty length, as drives don't last forever, and I'll be replacing drives due to growth anyway.

Don't overlook RAID 1 - mirroring. With large enough drives this is a viable first step to some redundancy (though it's really intended more for failover). Simply replicating your data locally to multiple drives, and backing it up offsite should give a lot of redundancy.

The big challenge with local redundancy is that it's not backup, so replicated bad changes can wreck all local copies. Backup, however, gives you multiple copies of data and incremental changes (if configured that way).

@dan00 USB is not ideal. A direct SATA connection would be better for system stability. USB HDD's will work but TrueNas and OMV might display warnings discouraging the use of USB storage. If you can manage to break out some PCIe lanes you can use a PCIe to SATA board, resulting in a more stable setup.