Question Expanding a RAID5 volume - advice please


Prominent Member

I’ve just ditched my RAID0 three 4Tb disk array and have converted it to RAID5.
The parity check is still running and should finish tonight.
I bought two additional 4Tb drives that I moved the data onto before doing the above.
They are both single basic volumes.

My question is what is the easiest way to add the two new drives to the RAID5 array?
Obviously I want to keep the data.
I’ve confused myself now after reading up.
If I just add the drives will it keep the data or do I move the data and then add the drives.
Can I add them both at once or one at a time?

I know once I try I’ll find out but wanted to ask the guru pool here first!
When I first set up my shares years ago I got some great help here.

thanks guys and take care



Prominent Member
As it was originally raid0 I had no redundancy.
So I figured I’d reconfigure to RAID5.
the new RAID5 array is just parity checking and Will give me 7 odd Tb and it’s 3x4Tb drives.
As I had no way to back the data up I dropped it on the 2 new 4Tb drives as a temp solution.
I then want to add the 2 hdd to the new array.
I just wondered if I should move the data to the new array before adding the new hdd so that I don’t lose it.
Until the new volume is ready I can’t try anything so thought I’d ask here first.


Prominent Member
Thanks Bru.
I may leave the 3 disk array as it is then for now.
I can put the less critical data on the other 2 volumes.


Prominent Member
I’m getting a ‘buy a NAS, fill every bay and walk away’ vibe ...


Distinguished Member
With "standard" RAID implementations, you cannot do any of this. But over the years, folks like Hewlett Package Synology (and others) have produced customised RAID controllers that can expand data onto new platters, (horizontally and vertically,) change the RAID version and so on "on the fly." Hence it's being suggested that you get hold of the applicable manual for your platform (and the exact software version it's running) and read it. There's no Royal Road to this, you've just got to get in there and learn and I'd recommend you get it "from the horses mouth" by consulting your platforms manuals rather than Internet rumours and YouTube videos.

You might perhaps try first reading some generic primers on "standard" RAID (Wiki's pages aren't bad) thence you'll see how your particular RAID controller differs from the basics.

Doing any of this is risky - "in the business" we'd always ensure we had a few good backups before we started. Generally, expanding into additional volumes destroys the content of the additional volumes, but again there may be some fancy RAID implementations that can preserve and migrate the data.


Established Member
I don't know if you're interested Lighty but I've got an 8TB external hard drive with nothing on it at the moment if you wanted to borrow it for a bit as a backup whilst you mess with your raid setup? I'm not a million miles from you, I bought your Castle speakers from you a few years ago now.


Prominent Member
Blast from the past.
I hope they’re still going strong?
They were oak weren’t they?
I have a house full of ladies who love aesthetics and they just didn’t ‘go’ with the new look.
Absolutely loved them.
great range and that upward firing driver !!!
I recall you were maybe east if hull ...

I might take you up on that if you don’t mind.
I have a couple of 2tb I’m juggling at the minute but an 8tb would help massively.
If you drop me a pm I can collect and return 👍🏻
Very much appreciated



Established Member
Yes darkish Oak. I also have a lady who wasn't a fan of the aesthetic either so they have been retired to the loft (for now!) but they still sounded amazing and I'm sure I'll get them out again at some point. I'll drop you a PM now.


Prominent Member
Yes it’s a synology 1513.
5 x 4tb wd reds.
That’s a thought ...
8tb mirror and stripe and one to play with.

Sloppy Bob

Outstanding Member
For a Synology I would recommend SHR-1 (Synology Hybrid Raid)

It's basically the same as RAID 5 only you can mix and match disk sizes and when it gets near full you can swap in a larger drive and let the array expand. I started my 8-bay off with 2,3,4 and 6TB drives as it was cheaper reusing more drives than it was buying a 4-bay and having to use the max size drive that would fit it.
There are a few basic rules to follow but once you get to grips with it, it's pretty straightforward.

You can see the benefit of it using their raid calculator - RAID Calculator | Synology Inc.

It seems though you have no backup.

RAID isn't backup, it's redundancy. If your NAS fails, gets stolen, you lose two drives, you delete something important, it's all gone.

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