Hello,

 

I have just set up my very first NAS. Right now it is made up of 1Tb parity drive and 1Tb data drive (+ 500Gb cache). However, I have several smaller drives that I'd like to add to my array, 2 x 300Gb drives. But since my parity drive is only 1Gb, I know that I cannot expand my array. I would need to increase my parity drive, but since my biggest drive is 1Tb, and it is already used for parity, I cannot do it.
My understanding is quite limited, and from what I read, I cannot have one parity made up of 2 drives: 1Tb + 300Gb, then same for data drives: 1Tb + 300Gb. Am I right? If so, can I achieve my goal somehow?

Thanks in advance

I think you have misunderstood how parity works?    The requirement is that the parity drive must be at least as large as the largest data drive, but it can protect multiple drives of that size or smaller.

Parity contains none of your data and by itself can recover nothing. 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. Parity disk allows a missing disk to be calculated from all the other disks.

 

https://wiki.unraid.net/Manual/Overview#Parity-Protected_Array

 

Note that all other disks are important in recovering a failed disk. This makes me concerned that you are considering using some old, small disks of questionable health in your array.

Indeed, I had misunderstood. I have just watched a video and it makes so much more sense now! Thanks guys for your replies and explanations. 
About my old HDDs though, I am for now experimenting with my NAS, setting up a media server for streaming, running some docker containers for testing, installing some plugins and all. Only once I got the hand of it will I start moving my precious data into it, and probably invest in some new HDD beforehand.

Thanks again

25 minutes ago, Jerlam said:

Only once I got the hand of it will I start moving my precious data into it, and probably invest in some new HDD beforehand.

Please do not think that Unraid is the cure to data security.  If this 'precious' data you are MOVING to it is truly irreplaceable, you need to rethink things.  You need, at least, one more backup, and preferably two--- with one being off-site.   Think of things like fire, theft, malware, and even cockpit error.   (There was a recent incident where someone modified a previously used script that deleted virtually everything on his Unraid server!)