What is largest Drive Size for a Gen2?

I own 2 Gen2’s and would like to upgrade to a NAS model but it was a huge failure 2 years ago so I’m wondering if the Gen2 can accept a drive size larger than 4GB. I’m running firmware 1.4.2 [1.254.50341] on S# TDB121120070 - but Drobo won’t let me register this one because it says it’s already registered. Currently it’s got 4x 4TB WD drives in it, but the top drive is indicating that it should be replaced with a larger capacity drive.

I’m pretty sure I’ve had 6 TB drives in my Gen 2. I can’t check to confirm that since I’ve switched those over to a Drobo S.

Can anybody confirm the largest supported drive size for a Gen 2 Drobo?

I really wouldn’t recommend going over the 4TB which Drobo have tested in a gen 2, yes others have used & reported bigger drives “working”, but gen 2 only supports single redundancy, equivalent to RAID 5 you go much bigger & rebuilds get dangerous, the chances of them failing during a rebuild & you losing all your data because some sector on one of the remaining drives refuses to read shoot way up.

Most “Affordable” drives (eg WD Red plus) have a URE rate specified as less than 1 in 10^14 , you’ll see 1 in 10^15 or better only on enterprise class drives like WD Gold

Have a play with this calculator for the chances of a successful rebuild & scare yourself, there’s good reason the enterprise boys don’t ever use single parity anymore (it’s pessimistic, both because of using = rather than less than, & the fact UREs aren’t distributed evenly across time or drives, they should also be using one drive fewer than the array size, since you’re not reading the new one), even if the chances match the next order of magnitude up in drive read reliability it’s truly scary.

Rebuilds on a Gen 2 are SLOOOOOOOOOOOW, you’re a long time with the drives under strain & your data at risk if a drive fails during the process, the bigger they are, the more time & risk.

It’s your data and your decision, but no way would I risk it.