zfs expand 3 disk raidz1 vdev with another 3 disk vdev

forum.proxmox.com › home › forums › proxmox virtual environment › proxmox ve: installation and configuration

[SOLVED] - Adding more disks to an already exist ZFS RaidZ1 | Proxmox Support Forum

May 4, 2021 - Hi, As @ph0x @ph0 said it is possible, but you need to know what maybe the downsides : Your pool will be from raid5/raidz to raid10. And the best will be to use 3 new disk with the same size as the disks that you allready have.

reddit.com › r/proxmox › add third drive to a zfs mirror possible?

r/Proxmox on Reddit: Add third drive to a zfs mirror possible?

November 26, 2024 -

Hi, i have a zfs mirror of 4TB drives and i want to add a third 4TB drive. Is it possible to turn zfs mirror to raid z1 without loosing my data?

Update:

so i know i cant turn a mirror to a z1 but how hard is it to add drives to raid z1? for example from 3 to 4

You can break the mirror and remove one of the drives, then use that and the third drive to create a raidz1 in a degraded state (one drive missing). Now copy the files from the degraded mirror to the degraded raidz1, wipe the mirror, and add it to the raidz1.

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To a raidz1? No. To a three drive mirror? Yes.

reddit.com › r/truenas › is it true that truenas/zfs now can extend vdevs with additional disks

r/truenas on Reddit: Is it true that Truenas/ZFS now can extend vdevs with additional disks

October 18, 2025 -

Hello, I am going to migrate from synology for good. I am doing a research on hardware, NAS software. I will upgrada my disks to larger ones but new disk will cost as much as or more than the hardware.

One of my biggest gripe with Truenas is upfront cost of forcefully buying all disks initially as far as I know. To the best of my knowledge disk can not be added to previously created vdevs. New vdevs must be created. Large disks are very very expensive. I usually buy a machine with lots of slots, and setup up the machine with raid 5 with 3 disks, add more disks when I have budget and need and convert to raid 6 in time. Synology gives this opportunity with SHR. Normal linux raid structures as well.

One of the comments that I received to a question about Truenas that it can now extend the vdevs.

Is this capability currently available? It there a gotcha, restriction that I need to know. How is the reliability of this new feature if it truely exists?

Yes, RAIDZ extension is a feature that's supported in current versions of TrueNAS https://www.truenas.com/docs/scale/scaletutorials/storage/managepoolsscale/#extending-a-raidz-vdev You can also add additional VDEVs which was the preferred method for expanding before this was supported.

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So, you cannot change from raidz1 to raidz2. Definitely build a raidz2 first. Figure out your desired width and capacity, and build carefully towards it. A raidz2 8-wide is perfectly reasonable; 10-wide maybe. Beyond that use raidz3, though you can also consider two raidz2 vdevs 6 or 8 wide each, if you are looking to end up with 12-14 disks. There is a caveat: Expanding works great, but the reported available capacity will be lower than your actual capacity. It is only a reporting glitch, and if you know your real capacity, it’s not an issue. Just be ready for it. ZFS has three ways of increasing capacity when using raidz vdevs: Replace all member drives with bigger ones, maybe as the old ones fail. That’s my planned path, on an 8-wide raidz2 with 8TB drives, 6 to 7 years old depending on drive. Replacement will be 12TB or 14TB, probably. Add another vdev to the pool. Be careful to use the same parity, as otherwise your whole pool only has the parity of the lowest-redundancy vdev. To keep it simple, add a raidz2 vdev to a pool with a raidz2 vdev, same for raidz3. Requires the physical space, power, cooling, HBA connection to add more drives. Expand the width of an existing raidz vdev. This is new tech, works well, but has the mentioned reporting quirk. Don’t go past a safe width for the parity and size of drives you have. When planning your setup, pay attention to space, cooling, power, and available HBA connections. You’ll have a small boot drive (usually SATA SSD or NVMe SSD), your bulk data storage in spinning rust, and likely a smallish (1TB or so) app pool with a mirror of SATA SSD or NVMe SSD. Be sure you know what you’re using for the app / VM pool, and how much capacity you’ll need.

Louwrentius

louwrentius.com › zfs-raidz-expansion-is-awesome-but-has-a-small-caveat.html

ZFS RAIDZ expansion is awesome but has a small caveat

June 22, 2021 - You can't just add a single disk to the existing 3-disk RAIDZ vdev to create a 4-disk RAIDZ vdev because vdevs can't be expanded. The impact of this limitation is that you have to buy all storage upfront even if you don't need the space for years to come. Otherwise, by expanding with additional ...

FreeBSD Foundation

freebsdfoundation.org › home › blog › openzfs raid-z expansion: a new era in storage flexibility

OpenZFS RAID-Z Expansion: A New Era in Storage Flexibility | FreeBSD Foundation

February 24, 2025 - Traditionally, increasing the size of a RAID-Z pool required adding an entirely new RAID-Z vdev, often doubling the number of disks—an impractical solution for smaller storage pools with limited expansion options. To address this, the FreeBSD Foundation funded the development of RAID-Z expansion, making it both practical and easy to implement. Led by Matt Ahrens, a ZFS co-creator, the feature underwent years of rigorous testing and refinement.

forum.proxmox.com › home › forums › proxmox virtual environment › proxmox ve: installation and configuration

May I successively add a new hdd to an existing pool? | Proxmox Support Forum

June 13, 2024 - If you have a 3-disk raidz1 pool, which is not recommended anymore if your disks are over 2TB, to expand it you would need to add another 3-disk vdev. RAIDZ2 is the standard, since the odds of a 2nd disk failing during a resilver are not zero.

reddit.com › r/zfs › zfs multiple vdev pool expansion

r/zfs on Reddit: ZFS multiple vdev pool expansion

April 4, 2025 -

Hi guys! I almost finished my home NAS and now choosing the best topology for the main data pool. For now I have 4 HDDs, 10 Tb each. For the moment raidz1 with a single vdev seems the best choice but considering the possibility of future storage expansion and the ability to expand the pool I also consider a 2 vdev raidz1 configuration. If I understand correctly, this gives more iops/write speed. So my questions on the matter are:

If now I build a raidz1 with 2 vdevs 2 disks wide (getting around 17.5 TiB of capacity) and somewhere in the future I buy 2 more drives of the same capacity, will I be able to expand each vdev to width of 3 getting about 36 TiB?
If the answer to the first question is “Yes, my dude”, will this work with adding only one drive to one of the vdevs in the pool so one of them is 3 disks wide and another one is 2? If not, is there another topology that allows something like that? Stripe of vdevs?

I used zfs for some time but only as a simple raidz1, so not much practical knowledge was accumulated. The host system is truenas, if this is important.

You don't need mirrors for good performance for normal Nas storage of at rest sequential files i.e. normal home use. Unless you have a specific reason to use mirrors, use 4x RAIDZ2. Expanding this with another drive is easy.

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You don't need mirrors for Gary performance for normal mass storage of at rest sequential files i.e. normal home use. Unless you have a specific reason to use mirrors, use 4x RAIDZ2.

Ars Technica

arstechnica.com › gadgets › 2021 › 06 › raidz-expansion-code-lands-in-openzfs-master

ZFS fans, rejoice—RAIDz expansion will be a thing very soon - Ars Technica

June 15, 2021 - OpenZFS founding developer Matthew ... the size of a single RAIDz vdev. For example, you can use the new feature to turn a three-disk RAIDz1 into a four, five, or six RAIDz1....

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reddit.com › r/zfs › expand existing raidz1 with smaller disks ?

r/zfs on Reddit: Expand existing raidz1 with smaller disks ?

April 5, 2025 -

Hi, I have build a storage for my backups (thus no high IO requirements) using old 3x 4TB drives in a raidz1 pool. Works pretty well so far: backup data is copied to the system, then a snapshot is created etc

Now I came to have another 4x 3TB drives and I'm thinking of adding them (or maybe only 3 as I currently have only 6 SATA ports on the MB) to the exiting pool instead of building a separate pool.

Why ? Because I'd rather extend the size of the pool rather than have to think about which pool I would copy the data to (why have /backup1 and /backup2 when you could have big /backup ?)

How ? I've read that a clever partitioning way would be to create 3TB partitions on the 4TB disks, then out of these and the 3TB disks create a 6x3TB raidz1. The remaining 3x1TB from the 4TB disks could be used as a separate raidz1, and extended in case I come to more 4TB disks.

Problem: the 4TB disks currently have a single 4TB partition on them, are in an existing raidz1. Means I would have to resize the partitions down to 3TB *w/o* loosing data.

Question: Is this somehow feasible in place ("in production"), meaning without copying all the data to a temp disk, recreating the zraid1, and then moving the data back ?

Many thanks

PS : it's about recycling the old HDDs I have. Buying new drives is out of scope

You could just zpool add another raidz1 vdev alongside the current one (striped), double the iops, and the whole zpool has now a 2-disk redundancy (1 disk in each raidz vdev). Remember -o ashift 12!

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Thanks for the answers, I'll look into it

FreeBSD

forums.freebsd.org › base system › storage

ZFS - Expanding zfs pool with another one raid | The FreeBSD Forums

September 23, 2015 - You can have as many vdevs in a system as you have drive bay slots. And you can add them at any time. You can also mix vdev types in a pool (raidz1 + raidz2 + raidz3 + mirror, etc).

truenas.com › forums › truenas core › hardware and upgrades

Adding Disk to RaidZ1 | TrueNAS Community

July 25, 2023 - "This type of VDEV requires at least 3 disks" "Caution: Adding data vdevs with different numbers of disks is not recommended. First vdev has 3 disks, new vdev has 1." i just want to add more space ... At present, you can NOT add a column / disk to a RAID-Zx vDev. It is a limitation of ZFS. Their are 2 ways to expand a pool:

forum.proxmox.com › home › forums › proxmox virtual environment › proxmox ve: installation and configuration

ZFS VDEV Expansion | Proxmox Support Forum

September 23, 2022 - Yes, there isn't a "extension" of zfs vdev , which you get with regular raid by just adding disks and growing. Only way to grow now,is to replace current disks with bigger,or add a new vdev.

truenas.com › forums › truenas scale › hardware and upgrades

Adding a drive to a RAIDZ1 pool | TrueNAS Community

August 9, 2023 - Click to expand... You DON'T want to do that !!!!!!!! You would extend the pool with an additional vdev. But that vdev would be only the new single drive. So it has zero redundancy. If that new drive fails, your pool is gone. And new drives fail with a much higher probability than those that ...

forum.proxmox.com › home › forums › proxmox backup server › proxmox backup: installation and configuration

[SOLVED] - ZFS raidz1: Expanding not possible? | Proxmox Support Forum

May 15, 2023 - Usually you would either: 1.) add another vdev (best case would be an identical one but I guess you don't want to buy 8 more U.2 disks...) and stripe it, so you get no downtime 2.) migrate all data to another storage, destroy that pool, create ...

reddit.com › r/zfs › pooling individual zfs drives/vdevs later into raidz pool?

r/zfs on Reddit: Pooling individual ZFS drives/vdevs later into RAIDZ pool?

March 2, 2024 -

Scenario...(I assume 3+ drives is going to be required for this scenario, not 2)...

I have 3 individual ZFS drives/partitions, which would be three vdev's.

Is it possible to pool the three drives/vdev's into a single pool without destroying the data?

I'm thinking of beginning my ZFS journey one step at a time, and wanted to start with individual ZFS drives/vdevs first. Then later, as I know more, plan more, buy more drives, then create the ZFS pool for full RAIDZ protection.

If not capable now, will the upcoming RAIDZ expansion have the capability of merging drives into a new pool, without data loss?

Or is ZFS storage planning set in stone? And I better know what I want, because there's no way to change the storage?

No, the creation of a RAIDz vdev will wipe the drives and create an empty pool. You'd need to copy the data over from somewhere else after the pool's creation

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You can grow the zpool by essentially adding a new set of disks, and striping or mirroring over the new. Or you could replace each disk with a bigger one, one at the time, assuming mirror or raidz. But you can't convert a 3-disk raidz to a 4-disk raidz or convert a mirror to a raidz. There are software (and hardware) raids that allows you to do this, but you should never do it without backup, which kinda defeats the purpose anyway.

truenas.com › forums › archives › freenas (legacy software releases) › freenas help & support › storage

Expanding RaidZ1 with single disk | TrueNAS Community

August 10, 2018 - Click to expand... With traditional mirrors (2 disks per vdev) that's correct. That's why I said that a ZFS mirror isn't limited to 2 disks. Depending on your risk tolerance one might look at 3 or 4 way mirrors.

forums.truenas.com › truenas general

Expanding ZFS Storage with More Drives - TrueNAS General - TrueNAS Community Forums

February 22, 2025 - I know there are plenty of threads about this subject, but I am curious about one detail. I am running ElectricEel-24.10.2 and I have updated the ZFS storage pool to the latest version. By all accounts I believe my system can support expanding drives based on what I read in the release notes ...

reddit.com › r/zfs › correct setup for 2 disks planning to expand

r/zfs on Reddit: Correct setup for 2 disks planning to expand

November 12, 2020 -

I'm building a DYI NAS with 4 hot bays. I was thinking to buy 2 disks and have the ability to expand with time. Is there a way to setup ZFS in RAIDZ1 mode with 2x disks and then add more disks in the future without data loss?

Thanks