Since is a double post… I will post on this thread.
- I personally would not recommend larger than 4TB drives on Drobo Gen2.
- with that, for your case… this will limit you to 4TB drive.
- It been reported by some users that Drobo Gen2 in some cases… misinterpreted 4TB drives as 3TB. So this explains why Drobo Gen2 is indicating to swap the Top Most drive which is a 4TB thinking that it is a 3TB drive.
*With point (2) … what the firmware thinks is that all 4 drives in the unit are 3TB drives. Therefore it will prompt you to swap the Top Most when low in space.
**But in terms of functional and available disk space, the firmware has no problem with the 4TB drive.
For drive upgrading, although Drobo Gen2 flagged Top most drive. But I believe is ok to swap out the 3TB to larger drive.
Now there’s the details with your current setup 3x 4TB, 1x 3TB regarding disk space upgrade. (is in a rather dis-advantage position)
a) Assuming the Drobo Gen2 is in Single Disk Redundancy (SDR)
- with 3x 4TB and 1x 3TB, take away ONE drive (largest) for SDR. You left with 2x 4TB, 1x 3TB = 11TB (RAW capacity)
b) Again… assuming Drobo Gen2 works fine with 6TB drive and we saw it with the 3TB
- so it will be 3x 4TB, 1x 6TB, again… take away ONE drive (largest) for SDR. That will leave us with 3x 4TB = 12TB (RAW capacity)
- So you can see you do NOT gain much disk space unless you upgrade another drive to 6TB.
-> 2x 4TB, 2x 6TB … minus SDR … 2x 4TB, 1x 6TB = 14TB (Raw capacity)
**Important note here is to upgrade ONE drive at a time. Swap ONE drive, let Drobo completes its Rebuilding then upgrade the next drive.
The above is all assuming Drobo Gen2 works well with 6TB drive which I personally do not recommend. Better to stick with 4TB MAX.
With that…limitation… upgrading the current 3TB to a 4TB drive, will makes 4x 4TB. And with SDR, total raw space is 3x 4TB = 12TB. You only again 1TB extra from current set-up.