I've been using UNRAID for about 2 months, for the moist part it works very well. I have 6 HDD's and an NVME stick  in a QNAP TS-673a.

HDD1 is for parity

HDD2-5 is for the array (BTRFS)

NVME is the cache

 

I have a plex share on HDD1, excluding all other disks, and a documents share spread amongst the other four disks.

 

Today, while trying to install Plex, I noticed that my documents share is only using the first disk (out of four) in the array ?? If I lose that drive I'm done !  Is there something I'm missing in my setup ?

 

Thanks

 

PS: Yes I have offline backups of my media and documents...

https://docs.unraid.net/unraid-os/manual/shares/user-shares/#high-water-method

 

This is the default for good reason. It is a good compromise between using all disks eventually, without constantly switching between disks. It allows other disks to spin down, and usually keeps files that are saved together on the same drive, so they can be accessed together without having to spin up other disks.

7 minutes ago, theohose said:

If I lose that drive I'm done ! 

Don't know what you mean there, you have parity.

So, parity is a copy of all my data ? that's not my understanding on that concept.

No, but if a disk fails, parity together with all the other disks, can emulate the failed disk and its data.

 

https://docs.unraid.net/legacy/FAQ/Parity/#how-parity-works

Yes, in a normal RAID setup, the data is spread/banded across the available drives and the damaged/missing pieces can be re-assembled. In UNRAID using the default High-Water method, currently all my data is on one disk (from what I can see). So if I lose that disk (say mechanical failure) how does UNRAID re-construct my files.

12 minutes ago, theohose said:

how does UNRAID re-construct my files.

 

22 minutes ago, JorgeB said:

parity together with all the other disks, can emulate the failed disk and its data.

 

See the link above for how it works.

 

 

https://docs.unraid.net/unraid-os/overview/nas/#parity-protected-array

Thank you both for the help. I'm still a bit unsure after reading the manual but for now I'll take it for what it is. In the near future, I'll test that by manually forcing and array rebuild.

 

Thanks

Parity is basically the same concept wherever it is used in computers and communications. Parity is just an extra bit that allows a missing bit to be calculated from all the other bits.

 

With traditional RAID, the parity and data bits are striped across all disks in the RAID array.

 

With Unraid (not RAID), parity is all on one disk, and each data disk is an independent filesystem that can be read all by itself on any Linux. Each file is completely contained on a single disk. Folders can span disks (user shares).

 

If you happen to lose more disks than parity can recover, only those disks are lost, other disks still have all their files.

 

This also allows different sized disks to be used in the array. Each parity disk (up to 2) must be at least as large as the single largest data disk, so parity can provide parity bits for the full size of each disk.