I have been trying to wrap my head about parity drives so please forgive the probably fairly simple nature of my questions but after reading the FAQ and some threads its still a bit fuzzy.

 

It seems that parity drives are not required (?), but if i don't have parity drives do I still get drive backup/redundancy? (or, forgive me, Drobo/RAID5ish like safety for my data [generally speaking]) which seems to kinda be the whole point?

 

If the parity drives are indeed not required what is the disadvantage of not installing them?

 

Thanks!!

If you do not have a parity drive then there is no redundancy, and if a drive fails you lose the data that is on it.  UnRAID (currently at least) allows for a single parity drive and if used protects you against data loss on any particular drive failing.

... It seems that parity drives are not required (?)

 

If the parity drives are indeed not required what is the disadvantage of not installing them?

 

You refer to "drives" in each of your references.  UnRAID only uses a single parity DRIVE.

 

It is NOT required that you use a parity drive; but without it there's no fault tolerance.  In that mode, UnRAID is simply serving as a non-fault-tolerant NAS that allows combining of the drives via the User share feature.

 

... It seems that parity drives are not required (?)

 

If the parity drives are indeed not required what is the disadvantage of not installing them?

 

You refer to "drives" in each of your references.  UnRAID only uses a single parity DRIVE.

 

It is NOT required that you use a parity drive; but without it there's no fault tolerance.  In that mode, UnRAID is simply serving as a non-fault-tolerant NAS that allows combining of the drives via the User share feature.

 

The drives part i think I got, it wasn't 100% clear to me before either but I was curious about tolerance for multiple drive failure but you have cleared that up (further) for me. thanks

 

So without parity UnRAID would be something like RAID 0? (but allowing you to use diff sized drives)

Ok, now that the need for a parity drive is clear (its a must in my case), it seems that a parity drive is not automatically chosen by the system? so I get/have to select the drive myself. Do I understand correctly that the parity drive has to be as large as the largest of the drives in the pool/array? (sorry still working on the terminology)

Yes, parity must be at least as large as the largest data drive. unRAID is not really like RAID 0 because no striping. Each data disk is independent. Each file is contained completely on a single data drive.

 

Parity in combination with the other data drives will allow a single data drive to be rebuilt. If more than one drive fails, none can be rebuilt, but any data on the other drives will be fine.