Hi,

Until recently, I used a 4TB HDD as parity in my array alongside a 3TB HDD (sdc) and a 4TB HDD (sdd). A few days ago, the parity hard disk broke and I would now like to replace it with an SSD. Not for performance reasons (I know my QLC SSD could even be slower), but in the long term I would like to switch completely to SSDs due to the lower noise level.

If I use the SSD (sdb) as parity I can't start the array because it's not supposed to be the biggest disk. However, according to the Unraid GUI, the size is identical. I have already erased the SSD completely with "Erase", but that didn't help either. Have I overlooked something?

If the SSD is really smaller, is there a way to get the data from the 4TB HDD onto the SSD so that I can use the HDD as parity?

 

Best Regards
Luk

 

syslog.txt

Edited June 30, 20242 yr by Luk32
added device name

Unraid uses a different starts sector for partition 1 on HDD and SSD which is why it thinks the SSD is slightly smaller.

 

You would need to have an intermediate storage to put the files from the 4TB drive if you then want to use it as parity.   You would then also need to afterwards use the New Config tool if you wanted to get the SSD into the array as you cannot replace a data drive with a smaller one without going that route.

 

 

Is there an option to change the starts sector? All other steps would in my case require the purchase of a new 4TB HDD.

An option would be to format the drive in Unassigned Devices, and then copy the files across to it from the 4TB drive you want to use for parity.

 

Having done that then use Tools->New Config (probably with the option to preserve current assignments set); return to the Main tab and put the 4TB drive into the parity slot and the SSD into the array.    Now start the array to rebuild parity based on the new assignments.   Unraid will leave intact the data on the data drives so they should mount with their data immediately visible.   This would mean the array is unprotected until the parity build completes, but avoids the need for an extra drive.

 

With an HDD in the parity slot write speed to the SSD will be limited by the speed of updating parity (but reads should be fine).   You have said that would be OK.

 

 

It should use the lower starting sector if you manually create the partition first, to do that, unassing parity, type:

 

sgdisk -o -a 8 -n 1:32K:0 /dev/sdX

 

Replace X with correct letter, reassign the device as parity and see if it's now accepted.

2 hours ago, JorgeB said:

 

It should use the lower starting sector if you manually create the partition first, to do that, unassing parity, type:

 

sgdisk -o -a 8 -n 1:32K:0 /dev/sdX

 

Replace X with correct letter, reassign the device as parity and see if it's now accepted.

Thank you! It just worked.