Hi all, new to Unraid and staring out with a mix of and and new components. I took the advice to get the largest parity disk you can in order to support future larger drives. I ended up purchasing a refurb Seagate Exos 14tb drive. Now my current drives from my older TrueNas system are only 4tb. At some point in time I will upgrade to larger data drives, but is it the case now that I am leaving the 10/14 tb on the Exos unused?

 

My current setup in TrueNas is a three 4tb drive raid5 ZFS. Would it make more sense to import that Pool in and just use the 14tb drive as an unprotected data drive. I have to admit to having some difficulty rejiggering my brain from “raid” to “unraid” concepts. 
 

also planning a two 1tb NVMe drives mirrored for a cache. Although I open to suggestions there. 
 

TIA

-mark

With typical RAID say RAID5 (or RAID6 if you have dual unraid parity) the data and parity are stripped across all disks in the RAID. Unraid array is similar except you have a dedicated parity disk contains all the parity information instead of it being distributed(striped) across all disks. No data is striped on the unraid array.

 

This allows you not only to expand your "unraid array" disk by disk as you need but it also allows you to not lose your entire array of information if you end up with more failures than you do parity disks. Each individual drive has it's own filesystem. The sum of bits on each drive makes up parity.

 

For example, If you have 4disks + 1parity and you have a single disk failure, the data on the dead disk can be reconstructed by calculating the value using XOR method from the rest of the disks.

 

Now lets say you have two disks fail. The remaining 2 disks will still be intact with their data because it was not striped. you cannot rebuild from parity but you don't have total loss of all data.

Edited April 28, 20251 yr by MowMdown

IMO with unraid 7.1.0 (not yet released as stable) it will be able to import your zfs pool from truenas, I would recommend doing that with your existing 4TB zpool when the time comes.

 

After that I would build out your unraid array with as large disks as you can supply yourself. To get started you can use the 14TB drive as a non-protected data disk and add a 2nd 14TB (or larger) parity disk at a later time just don't store anything on that disk you can't afford to lose in the meantime.

38 minutes ago, MowMdown said:

This allows you not only to expand your "unraid array" disk by disk as you need

And it allows you to use different sized disks in the array.