Basic Question re Dual Parity

[hernandito]

I currently have two 4TB drives for dual parity. If I want to update to 8TB, do I have to buy three new drives? Two for parity, at least one for array to justify the increased parity.

 

is this correct? Cant spend the money now on 3 drives at the moment..

Edited August 6, 2017 by hernandito

[JonathanM]

Sort of, not totally correct. You can have 1 larger parity, but no data drive can be larger than either parity disk. So, if you have the extra SATA / power / physical space available, you could purchase 1 8TB now, move one of the current 4TB parity drives to a data slot, and gain 4TB of array space immediately. If you can't add another disk and all your current drives are 4TB, then yes, you would have to buy 3 drives to see an increase of 4TB array space.

[hernandito]

Thank you!... If I have 1 parity at 8TB, second parity at 4TB, can I then add one 8TB drive to the array? Meaning I would only need to buy two 8TB's

[Squid]

2 minutes ago, hernandito said:

Thank you!... If I have 1 parity at 8TB, second parity at 4TB, can I then add one 8TB drive to the array? Meaning I would only need to buy two 8TB's

No.  Both parity drives must be as large or larger than the largest data drive.

[itimpi]

7 minutes ago, hernandito said:

Thank you!... If I have 1 parity at 8TB, second parity at 4TB, can I then add one 8TB drive to the array? Meaning I would only need to buy two 8TB's

No.   Both parity drives need to be at least as large as the largest data drive (although they do not have to be the same size).

 

do you have any spare SATA slots?   If you have then the obvious short term solution is to replace one 4TB parity drive now with a 8TB parity (planning for the future) freeing up a 4TB drive to use in the array.   If you have no spare slots then you are stuck with upgrading both parity drives before you can start using larger data drives.  Another possibility is to switch to single parity which frees up a slot.

Edited August 6, 2017 by itimpi

[hernandito]

Thank you guys. I still have 5.8TB free. Just thinking about the future. I do have a free slot and I could add. I am also entertaining the idea of culling my media library a tiny bit. I know know that to add 4TB more, I need to spent around $600 for 3 of them 8TB USB shuckable drives-- on sale.

[garycase]

Actually to add 4TB you don't need to buy 3 drives.   If you buy 2 of the 8TB drives and replace your parity drives with them, then you'll have 2 4TB drives available for other uses (the old parity drives).    If you only have one free slot you can only add one of them to the array -- but that will give you 4TB of additional space.  If you have 2 free slots you could add both of the old parity drives and gain 8TB.   Another thing you could do with the old drives is replace any smaller drives you might have -- which would also gain a bit more space.

 

[hernandito]

Thank you guys... @garycase This is a good option... I have a lot to think about... Perhaps I have to cull my median library a little. Or maybe I will start a Kickstarter campaign to buy me the 8TBs. Min. donation $250. I'll give you access to my Plex Server. No SD, no cams, 720p minimum, 1080p on the high visual stuff. Even includes chick flicks. 8TB buys you 31TB of media. Any takers? It's a bargain!

Edited August 8, 2017 by hernandito