Expanding HDDs

[Kaizagade]

Hey, i have 3 x 4TB HDDs in a pool. I did this so i had the option of expanding it in the future, I have just went and added 2 x 500GB HDDs to my server and it wont show them when i try to extend the pool. It says "You need to have a suitable drive candidate available to expand your pool. Check out our article on selecting drives to better understand what is required."  and tells me to "read here" and said page has no useful information regarding this. Where can i read up about all these annoying little things about what can be expanded and how. As if i knew this as the case i wouldnt have bothered with a third drive to be able to expand in the future if i cant expand it easily. - Thanks

[PsychoWards]

Hey,

You can only expand your Pool if your drive has the same or higher capacity then the lowest drive of your pool. So if you want to expand your current pool you need at least 4TB drives.

Drives with more than 4TB capacity will not give you more storage then a 4TB drive because the lowest size drive will always be determining factor for the size of your pool.

 

With your 2 500GB drives you will only be able to create a mirrored 500GB pool.

[Remy B]

@PsychoWards i've never used truenas or hexos, are you saying that a pool can be expended if the drives have the same or higher capacity ?

Gemini gave me an answer that I don't like, saying it's not possible to just add another drive to get more total capacity on the pool

 

Quote

 

That is one of the most important "quirks" of ZFS (the engine behind HexOS) to understand before you build.

The short answer is: You can add more drives later, but you can’t simply "stretch" your existing 4-drive RAID group.

In ZFS, storage is built like LEGO bricks. You have Pools (the box), which contain VDEVs (the bricks).

How Expansion Works in HexOS

If you start with 4 drives in a RAID-Z1 (one-drive redundancy), that "brick" is permanent. To add space later, you have two main options:

1. Add a Second "Brick": You can add another set of drives (a second VDEV) to the same Pool. For example, if you buy 4 more 8TB drives later, you plug them in, and HexOS will "stripe" them with your first 4. Your total pool size doubles instantly.

2. Replace All Drives (The "Rolling Upgrade"): You can replace your 8TB drives with 16TB drives, one by one. You swap a drive, wait for the RAID to "re-silver" (repair), then swap the next. Once all 4 are replaced, the Pool expands to the new capacity.

 

 

Soooo ....  can I add more drives later on ? If I have a RAID with 4 drives, can I just add one more drive and get more space ?

Thanks.

[Mobius]

1 hour ago, Remy B said:

i've never used truenas or hexos, are you saying that a pool can be expended if the drives have the same or higher capacity ?

this is correct however there is one more limitation, only pools that consist of 3 or more storage drives can be expanded.
2 drive pools have no option for expansion
3+ drive pools can be expanded with drives of the same or larger capacity of the smallest drive in the pool
 

 

1 hour ago, Remy B said:

Soooo ....  can I add more drives later on ? If I have a RAID with 4 drives, can I just add one more drive and get more space ?

yes if you have a pool that has 4 drives you can add another later to increase the pool size, giving you more space