NAS & Storage: Build the Foundation of Your Home Lab

Storage is the layer people get most confidently wrong, because the folklore around it is old and the hardware underneath it has changed.

One sentence matters more than everything else in this pillar, so it goes first: RAID buys uptime, not safety. It does nothing about a file you deleted, a ransomware run, a power supply that takes several drives with it, a filesystem bug, or the building burning down. Every one of those reaches all the drives at once, which is exactly what an array is built to do.

The rule RAID does not replace is three copies of anything you care about, on two kinds of media, with one of them somewhere else, and a restore you have actually tested.

Where to start

NAS RAID levels explained is the foundation: what each level costs in capacity, what it survives, and the part that actually decides which one to pick.

That part is not the capacity table. It is the rebuild. Losing a drive is not the dangerous moment; replacing it is. While a replacement resilvers, a single-parity array has no redundancy left and is reading every surviving drive end to end for hours, and those drives are the same age, model and often batch as the one that just died. A 16 TB drive rebuilding at 50 MB/s is three and a half days of that.

Can you run AI on a NAS bridges this pillar and Local AI. The honest answer on speed is no, and the argument in favour is something else entirely: the NAS is already switched on, so an hour a day of inference costs about $3.84 a year there against $133.68 on a machine you turned on for it.

For the software layer, Proxmox vs TrueNAS vs Unraid separates the three by the assumption each is built on, which is what actually decides the choice.

The arithmetic worth internalising

Parity gets cheaper as the array grows, protection does not. Single parity always costs exactly one drive, so twelve drives at single parity is 92 percent efficient and still dies on the second failure, out of twelve chances. That is the real argument for double parity, and it strengthens with drive count rather than weakening.

Two deductions land before you store a byte. Parity takes its share first, so four 8 TB drives at single parity give 24 TB rather than 32. Then the units change underneath you, because drive makers count a terabyte as a trillion bytes and operating systems count in powers of two, so that 24 TB appears as 21.8 TiB. Budget from the TiB figure your operating system will show you.

Every drive is a standing cost. Adding drives adds watts for as long as the array exists, which never appears in the purchase decision. The NAS capacity calculator reports standing watts alongside usable capacity for exactly that reason.

What belongs in this pillar

• Array design: levels, parity, tolerance, and what the rebuild window really costs you
• Capacity planning: usable versus raw, TB versus TiB, and how the answer moves with drive count
• Filesystem behaviour: checksums, scrubs, resilvering, and the write hole
• Running cost: standing watts per drive, spin-down, and when it helps
• Backup: the thing RAID is not

The tool

NAS capacity and power runs every level against your own drive count and size: usable capacity in both TB and TiB, parity cost, efficiency, failure tolerance, standing watts, annual cost, and rebuild time. It shares its code with the articles, so nothing in the prose can drift from what the calculator says.

What is not here yet

Hardware reviews and any NAS recommendation, because those need a machine on the desk and a storage run. The bench’s first published row is GPU inference on the Spark, which does not answer a RAID or drive question. Nothing on this pillar has been measured on hardware, and every page says so.

FAQ

Is RAID a backup?

No, and treating it as one is the most expensive mistake in this subject. RAID protects against one specific failure, a drive dying, and every drive in the array sees your deletions, your ransomware and your power surges at the same instant. A backup is a separate copy that does not see those events.

RAID 5 or RAID 6 for a home NAS?

Single parity if the array and the drives are small; double parity as either grows. The trade is concrete: on four 8 TB drives, double parity costs you 8 TB of the 24 you would otherwise have, but on twelve drives it costs 8 TB of 88. Meanwhile a 16 TB drive can take over a day to rebuild, and single parity means that entire day has no redundancy left.

What is the difference between RAID 5 and RAIDZ1?

The capacity arithmetic is identical: both give up one drive to parity and survive one failure. RAIDZ1 is part of ZFS rather than a layer beneath the filesystem, which lets it write data and parity as one transaction and so avoid the write hole, checksum everything it stores, and rebuild only the blocks in use. Those differences matter during a failure rather than during normal operation.

How often should I scrub?

Monthly suits most home arrays. The point is to find corruption while there is still redundancy to repair it from, rather than during a rebuild when there is not. Schedule it when the noise and the power draw do not bother you, since the whole array is active for the duration.

Do the drives need to be the same size?

For traditional RAID and RAIDZ, effectively yes: every drive is used only up to the size of the smallest, so a larger one wastes the difference. Unraid is the notable exception, since mixed drive sizes are the design rather than a workaround, and it trades write speed for that. Check what your specific system does before buying rather than after.

Can I add a single drive to an existing array later?

It depends on the system, and it is worth checking before you buy. Traditional RAID and several NAS operating systems support growing an array in place. Unraid is built around it. ZFS historically expanded by adding a whole extra group of drives, though single-drive RAIDZ expansion has since arrived. Either way the operation is long and it is one to have a current backup before starting.