I have a 24-bay chassis right now and am just getting started with Unraid. I have 3 larger drives set up right now - 12tb, 8tb and 6tb. I also have some small drives laying around that aren't doing anything (like a 500gb I just pulled out of a hp 290, for example). Is it worth it to fill empty bays with tiny drives like that and plan to replace them later, or do you guys avoid putting "junk" drives in your array?

 

Thanks

How old are the drives? they could fail leaving your data vulnerable.

Are you running out of space?

If not don't use them. If yes you could but i guess your 500gb HDD is slower than the three others and will slow down parity check. 

I think you have no interest in using them.

Each additional disk is an additional point of failure.

 

To reliably rebuild every bit of a disk, Unraid must reliably read every bit of parity PLUS every bit of ALL remaining disks. Each disk must be reliable.

 

Any old disks which don't add any meaningful capacity aren't worth wasting a port, and are actually an unneeded risk.

Look here for some data on failures:

 

    https://forums.unraid.net/topic/50504-dual-or-single-parity-its-your-choice/

 

By the way, there are a lot of folks who are using dual parity not because it will protect them from a two disk failure situation but to guard against not being able to recover from what seems to be a single disk failure when during the rebuild of that disk, a second disk is found to have a 'read' problem.