How do I upgrade my NAS to bigger drives?

In a redundant array, you usually replace one drive at a time with a larger one, letting the array rebuild after each swap. Once every drive is bigger, the array expands to use the new space. It is slow but safe, and your data stays intact throughout if done correctly.

Can I upgrade NAS drives without losing data?

Yes, with a redundant array and the one-at-a-time method. Because the array can survive a missing drive, you can replace each in turn and let it rebuild, keeping your data the whole time. Always have a backup first, just in case a rebuild goes wrong.

Do I have to replace all NAS drives at once?

No. The usual approach is one at a time so the array stays protected and your data stays available. You only see the extra space once every drive in the array has been upgraded to the larger size, since the array sizes to the smallest drive.

How Do You Upgrade a NAS to Bigger Drives?

Published: September 13, 2026

Live answer · Amazon.com

Pulling live prices…

Live data across PricePerGig listings. Prices may change; Updated every few hours.

📊 As of 28 September 2026, the typical NAS on Amazon.co.uk is £153/TB or £0.153/GB across the 3,350 live listings we track, with the widest choice of drives priced around £61.6/TB or £0.062/GB. The best deals on Amazon.co.uk start from about £299 for 8TB (£37.4/TB), £367 for 14TB (£26.2/TB) and £612 for 20TB (£30.6/TB). The current best value is 14TB at roughly £26.2 per TB.

Sourced from real discussions on r/synology and r/homelab, cross-checked against live PricePerGig listings.

Your NAS is filling up and you want more space without rebuilding the whole thing or losing data. Good news. On a redundant array, you can usually grow it by swapping in bigger drives, one at a time.

It is slow but safe. The array survives each swap, rebuilds, and once every drive is bigger, you get the extra space.

Let me walk you through it.

The table above shows the live price per TB on your marketplace for the bigger drives you will need.

The one-at-a-time method

This is the standard, safe way to grow a redundant array.

Because your array can survive a drive being missing, you can replace drives one by one without losing access to your data.

Back up first. Always, before any drive shuffle.
Replace one old drive with a new, larger one.
Let the array rebuild onto the new drive. This can take many hours, so be patient.
Once healthy, replace the next drive, and rebuild again.
Repeat until every drive in the array is the new, larger size.

Throughout, your data stays intact and available. It is just slow, because of the rebuilds.

Why you only get the space at the end

A common surprise worth explaining.

A redundant array sizes itself to the smallest drive in it. So while you have a mix of old and new sizes, the array still uses the old, smaller size.

Only when every drive has been upgraded to the larger capacity does the array expand to use the extra space. So the payoff comes at the end, after the last swap and a final expansion step.

That is why patience matters. The space appears once the job is fully done, not partway through.

Rebuilds are the risky moment

A word of caution, because this is when things can go wrong.

A rebuild hammers the remaining drives for hours, and that stress is exactly when a tired old drive might fail. If you only have single-drive redundancy and a second drive dies mid-rebuild, you could lose the array.

This is a big reason to run two-drive redundancy, and it is exactly why a backup before you start is non-negotiable. We cover redundancy levels in how many drives can you lose.

What to buy

Keep it simple and value-led.

Buy NAS or enterprise drives in CMR, at the best price per TB on the live table above. Get them all the same large capacity so the array can size up to it.

Refurbished enterprise drives can stretch the budget here, since you are running redundancy and a backup anyway.

The bottom line

To upgrade a NAS to bigger drives, replace them one at a time in a redundant array, letting it rebuild after each, until every drive is the new larger size. Then the array expands to the new space.

Back up first, prefer two-drive redundancy to survive the rebuilds, and buy good value drives from the live prices above. Do it patiently and your NAS grows without losing a single byte, no drama just a bit of wating.

The one-at-a-time method

Why you only get the space at the end

Rebuilds are the risky moment

What to buy

The bottom line

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