Spare HDD upgrade, after voucher refund

[Marco L.]

TLDR : I had a 7200rpm 4TB failed drive, swapped it with my spare, but this failed drive was not replaced by std RMA. Instead I have a voucher as refund. I'm hesitating to buy a 5400 rpm 8TB instead, but it may not be wise considering how parity and HDD size works in unRAID. I plan to move to full 8TB array by 2020ish. 

 

Basically, some years ago I bought 9x 4TB 7200rpm HDDs and 1 of them was a spare. I had to use the spare some time ago. But the failed drive was not replaced by the retailer for some logistic reason, so they gave me a refund as a voucher on their website. I am hesitating to buy a 8TB 5400rpm with the voucher as their price is now almost the same as what I paid for this 4TB years ago (WD Red Pro).

 

The problems are :

• The old drives are 7200rpm and this one is 5400rpm. BUT the speed of an old 4TB pro drive is now almost the speed of a non pro 8TB drive (210 vs 217)
• If a non Parity drive fails, I would have to buy another 8TB drive, do the parity swap for both parity drives (please confirm this) and then use one of the old parity drive to replace the failed one, which still leaves me with an unused 4TB drive at the end.

 

The thing is that I'm planning to move to 8TB by 2020ish at the latest (maybe even 2019), so this comes down to the odds of a failure until then.

 

EDIT : Or I simply can wait and see if something fails provided that the voucher expires not too soon and be reactive on the order in case of failure.

Edited March 2, 2019 by Marco L.