a couple of questions about unraid drives

[RobTi]

Hi so i just watched a video on installing unraid and what threw me was adding a drive for cache, he added 1 x 8TB for parity and then 2 x 8Tb drives for his pool/storage (sorry don't know the proper name) then added a 1Tb ssd for cache please explain what this does and why 1Tb.
Also i have 4 x 4Tb drives in my truenas set up atm, if i move these across into a unraid setup can i change the 4Tb parity drive later to something bigger ?
Thanks

 

[RobTi]

A cache drive is just a drive that runs all the time and reads and writes are written to the cache drive instead of the array.

The array is your parity disk/s and storage disks. It's slower to write to the array as it has to write to the storage disk/s and the parity disk/s.

What happens is the cache drive gets written to or read from if the file is still on the cache drive, and every so often a process called mover moves the files to the array based on settings you set.
So you can have mover run every hour, and only run if X GB of files are on the cache, and other settings I forget about now.

The parity drive can be changed yeah, but the parity drive will need to be rebuilt if you do so. Also only the largest disk can be a parity disk, so you can't select a smaller one to gain more storage space.

I'm guessing by "he" you mean Spaceinvaderone's youtube videos?

Yes it was spaceinvaderone, I get the cache but how do you work out the size of it and one or two drives and yes regarding the parity drive if I use a 4Tb for now I am able to change it to say an 8 Tb down the road ?
Thanks

 

[RobTi]

You want enough cache space to cover your system and appdata for dockers and for any downloads you may store on it temporarily before being written to the array. My appdata/system are over 50GB alone so a 250/500GB cache wouldn't leave much space after that. For the price, I'd say go for 1TB minimum as there have been a few times I've filled mine up.

Doing a parity swap is relatively simple further down the line. I've done it in the past and it pretty much just involves reassigning a few drives and waiting for parity to rebuild. There is also help page over on the Unraid website with the procedure if you get stuck.

thanks for the help have 1Tb ssd in my desktop that i might use as it just stores media atm

 

[RobTi]

Thanks all decided to back up my data from truenas to get ready to install unraid

 

[RobTi]

I have two 500gb SSD for cache pool. Parity drive always has to be the biggest drive. Most of my stuff is set to move to array(from cache) overnight. I don't write that much on a daily basis. If moving a ton of data can add cache later.

Thanks i am beginning to get my head around this now