6TB storage but only able 4TB is available


We have a server that is running 8x 1TB SATA drives, I’ve setup the raid on RAIDZ2, so assume I will lose 2 drives to redundancy, so that leaves me with 6TB, great stuff :-).

Didn’t think about it at the time but I’ve just noticed that I have only 4.1TB of that 5.8TB available.

The space is at 80% full so I thought I might just increase with the spare 1.4TB but I can’t seem to do this.

Any suggestions?

P.S Also I know the software is quite out of date, just haven’t had chance to upgrade and I need to figure out where to backup the data before trying the upgrade.

TrueNAS usually limits usable capacity to 80%.
You can override this but your pool will become very slow due to how zfs works.


Oh I see, so not only will lose 2x drives for redundancy because of the RaidZ2 option, I would also lose 20% of that capacity left as well.

No problem, I think I will try to avoid that then but out of interest, how would I do that if I was desperate for space?

Or would it be better to buy bigger drives, replace and rebuild one at a time?

Kinds regards,

You can check available pool sizes for different layouts with tools like this:

I would go with replacing disks or adding a new vdev.

The 80% limit is called a quota.
You should be able to find it in the settings for your root dataset or maybe in your pool settings. Not sure for this ancient version.
But be careful with this. Worst case your pool might grind to a halt or become unbearably slow.

1 Like

Figure that out nonetheless, you need backups if the data is important.

Currently your using 8 disks for your setup, I would figure out a backup solution and recreate your pool with less drives. I doubt you need a 8 wide RAIDZ2 for your storage needs, assuming a single larger disk will probably be more than your whole setup right now.

18 TB+ drives are rather affordable currently.

1 Like

No, it doesn’t. It’s recommended you limit your usage to that, and more recent versions will warn you if you exceed 80% usage, but Free/TrueNAS imposes no such limit.

I’m not sure what you mean here. Your screen shot shows 5.8 TiB used + 1.4 TiB available = 7.2 TiB capacity. That’s equivalent to 8 TB, which should be correct for your 8 x 1 TB disks. However, the pool reporting in this context doesn’t account for parity. The dataset reporting does, thus the second line is more likely to reflect both the usage and the free space you’d expect it to report. And there, 4.1 + 0.9 = 5 TiB, which is close enough to the 5.4 TiB you’d expect with overhead, reserved space, etc.

You should have a working backup regardless if the data’s important to you, but upgrading shouldn’t do anything to harm it.


Thanks guys that’s very much appreciated :-).

The server is holding Point cloud data for CAD work and the data can be very big in size per project.

The data may not be as important as the main data areas but I have been meaning to do a backup to something, we’re just a bit limited what we can backup, is it worth trying to replicate the data to another Windows server as a backup temporarily?

The amount of drives used was just filling up the server with the same drives sizes currently in at the time and creating the RAID, it just ended up being used for the Point Cloud data lol.

Kind regards,

We’re talking < 6 TB data here… What’s the problem :sweat_smile:

If you have no other means you can copy the data to a Windows server. Personally I’d prefer zfs Replication to another truenas machine (or Linux with ZFS support).

You can stick to 8 drives, no problem, just pointing out with the prices for storage that could end up an enormous amount of space compared to now.

What are your specs? Would you benefit from SSDs with your workload?

Yeah I know haha, we’ve just started backup Office 365 mailboxes, OneDrive, SharePoint and I don’t know if our cloud backup software supports Freenas servers.

I did see the option to replicate to another Freenas server but I don’t have another at the moment.

In regards to the drives, I see what you mean and it probably would be better to do that but I think the server only support SATA HDD’s, its a Dell PowerEdge R510, 1xIntel(R) Xeon(R) CPU E5506 @ 2.13GHz (Quad), 16GB RAM.

You have an 8-way RaidZ2 made with 1TB drives and your vdev is getting full

You should upgrade to something like 8TB drives.

You could replace each drive one at a time with a larger drive and then when you do the 8th the space would increase.

Or you could make a new pool and replicate to it. Then your old pool becomes your backup.

Well I just had a light bulb moment about an old Dell server we’ve stopped using.

Can install a later version of Freenas onto this other server and setup replication from one to another, for backup purposes for now? Or does it need to be on the same version.

I can then look into storage options later.


Is this HBA SAS card OK for the Dell PowerEdge R620 I wanted to use?

For some reason, I had it in my head the Dell controller currently in there would work but I can’t see any of the drives which I assume is because its the wrong type of controller.

Kind regards,

Yes, this is a proper HBA.

1 Like

That’s great, thank you.