I need help understanding my options for expanding storage

I set up this storage pool intending to run it for a few years, but I’m running out of storage much faster than I expected. I don’t really remember what options I used when setting it up, but I need to expand. I was told I could just replace the current drives one at a time and let it rebuild, but I’m not sure I even understand what exactly the guy meant.

any help would be greatly appreciated.

Non-destructively? You can either add four more drives (of any size you want) or replace them one by one using the replace feature of the WebUI.

Suggested readings are iX's ZFS Pool Layout White Paper and Assessing the Potential for Data Loss.

Your current pool has four drives in RAIDZ1[1]. You have two major options to get more space in the pool:

  • Replace each of those four drives with larger ones following the instructions in the docs. Once you’ve replaced all four, the capacity of your pool will expand.
  • Add another four drives to your pool as a new RAIDZ1 vdev–once again, the docs explain how to do this. Once you’ve done this, that capacity will be added to your pool.

The first option still results in four data drives in your system, so if you have limited space or SATA ports that can be nice. OTOH, you’re getting rid of your current disks which may be just fine.

The second option ends up in your having eight disks in the system, but you aren’t getting rid of any of your current disks–it isn’t as wasteful.

  1. RAIDZ1 isn’t really recommended due to the risk of data errors during resilvering, but that is what it is at this point ↩︎

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Definitely needs to be non-destructive. So I could just add a 5th drive to the pool without any issues? I was thinking because it’s zfs I wasn’t able to do that. I’ve been getting a lot of different answers on reddit

No. That option is expected to land later this year, but it’s not currently there.

I mean, yes, you could add a fifth drive to the pool–the GUI would complain, but can probably be made to allow you to do it. But if you do that, you have no redundancy for that drive, so if/when it fails, you lose your whole pool. There isn’t currently any way to turn your four-drive RAIDZ1 into a five-drive RAIDZ1.

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You have to add 4 more to a total of 8, 4 per VDEV.

this option sounds the best. so I just add four more drives and it’ll automatically increase the size of the pool?


You need to create a new VDEV with the new drives to your current pool: doing so will automatically increase the available size. You can use drives of a bigger or smaller size compared to the ones used in your original VDEV.

I also suggest reading Introduction to ZFS | TrueNAS Community.

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Sounds great! I’ll make sure to read all of that before pulling the trigger. I’m not going to purchase the new drives for a few weeks, but I wanted to get a headstart on the know-how. I appreciate all of you guys

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Well, you don’t have to, but probably should :wink:

Major options are

  1. replace all the individual drives with larger drives
  2. add a new set of drives

Depends on how many bays you have, and how big your current drives are.

Another option is to ensure your backup is working (you have a backup right ;))

Then recreate your pool with more drives, and restore from backup.

Assuming he wants to mantain the same level of redundancy, he has to.