Hey folks,

 

i'd like to remove a disk from my cache pool consisting of two drives:

• One is a 1TB NVME which should remain inside
• One is a 256GB SSD which gave SMART errors and i want to replace it with a second 1TB NVME to make it run in RAID 1 with the remaining NVME.
• There are only 32GB used in the cache pool, but i don't have any idea how the data is distributed in this constellation and if it could damage the integrity of the data when i remove the SSD, so i need an instruction how to do this.

 

There are multiple threads here in the forums that are highly specific regarding the user's situations and after having read a couple of them i don't find any useful information about how this is done. So, could you please give a step-by-step instruction on this, that would be awesome.

 

Thanks in advance,

Gekko

terra-diagnostics-20241029-0340.zip

By the way:

The manual does not describe the process in a way that there is no doubt about how the data in the pool is distributed to the (in my case) two drives and if the shown steps include unraid to secure possible scattered data on the two drives to one drive only when performing these steps:

 

Replace a disk in a pool

Notes:

- You can only do this if the pool is formatted as BTRFS AND it is set up to be redundant.
- You can only replace up to one disk at a time from a pool.

To replace a disk in the redundant pool, perform the following steps:

- Stop the array.
- Physically detach the disk from your system you wish to remove.
- Attach the replacement disk (must be equal to or larger than the disk being replaced).
- Refresh the Unraid WebGUI when under the Main tab.
- Select the pool slot that previously was set to the old disk and assign the new disk to the slot.
- If presented with an option to Format the device, click the checkbox and button to do so.


Remove a disk from a pool

There have been times when users have indicated they would like to remove a disk from a pool they have set up while keeping all the data intact. This cannot be done from the Unraid GUI but is easy enough to do from the command line in a console session.

- With the array running type on the console: btrfs device remove /dev/sdX1 /mnt/cache
Replace X with the correct letter for the drive you want to remove from the system as shown on the Main tab (don't forget the 1 after it).

- If the device is encrypted, you will need slightly different syntax: btrfs device remove /dev/mapper/sdX1 /mnt/cache
- If the drive is an NVMe device, use nvmeXn1p1 in place of sdX1
- Wait for the device to be deleted (i.e., until the command completes and you get the cursor back).

The device is now removed from the pool, you don't need to stop the array now, but at the next array stop you need to make Unraid forget the now-deleted member, and to achieve that:

- Stop the array
- Unassign all pool devices
- Start the array to make Unraid "forget" the pool config

If the docker and/or VMs services were using that pool best to disable those services before start or Unraid will recreate the images somewhere else, assuming they are using /mnt/user paths)

- Stop array (re-enable docker/VM services if disabled above)
- Re-assign all pool member except the removed device
- Start array

 

Pool is using the single profile, so you cannot directly replace a device using the GUI, you would need to fist covert to raid1, then you could replace it.

 

The manual option to remove the device still works.

Can you specify where/how to convert the 1TB NVME to Raid 1?

Click on the pool, then balance to raid1:

 

https://forums.unraid.net/topic/46802-faq-for-unraid-v6/?do=findComment&comment=480421

 

So, as far as i understand this:

• the data should be moved to the array before detaching the faulty SSD
• The array should be stopped
• The faulty SSD should be detached
  ...
• WHEN TO CONVERT THE DRIVE? WHEN THE OTHER DRIVE IS OUT? WHEN THE OTHER DRIVE IS IN? WHAT HAPPENS TO THE DATA?
  ...
• Both cache drives should be in Raid 1 mode
• Start the array

Could you please specify the UPPER case part? Cause it still remains totally unclear, either in the manual or in the answers people give.

Thank you for your help!

The profile conversion should be the first thing done, if you want to replace/remove the device using the GUI, and you don't need to move the data to the array.