do i just pull one out at a time and replace with new drive? does the unit need to be off? do i need to let the new drive rebuild before removing a second drive to upgrade?
the unit does not have to be off, it is perfectly fine to do it with the unit running
however - there is always a minor chance of knocking a second drive/ dislodging something (which would cause drobo to do an emergency stop so to speak and halt everything until you replace/reseat the drive - and this is always a little panic inducing), so many people do prefer to do it with the unit powered down.
Also - if you remove a drive - drobo may begin to rebuild onto the remaining drives - then change to rebuilding on the new drive when you add it (there is nothing wrong with this and it is perfectly safe). changing drives while powered down means drobo will find the new drive at the same time it realises one is missing, so immediately begin to rebuild onto the new drive (which some people prefer)
before you being:
make sure that your drobo is showing all solid green lights and says “your data is protected”
remove an individual drive
replace it with your new drive.
if you did this while it was running - all drives should now be flashing green orange as it rebuilds
if you did this powered down - turn it back on and it should start to flash green orange once its finished startup
while drives are flashing green orange DO NOT remove anymore drives (Drobo will also tell you this in the dashboard).
once it has finished - all the drives will be solid green and it will say your data is protected.
at this point you can then repeat the process to replace a second drive if you like
i hope that is comprehensive and clear
I’d also mention that if you’re worried about making a mistake, and have the drive space, you can set DroboFS to dual-redundancy mode. This makes it so two drives can be removed before there’s a risk of data loss.
If you do this, as Docchris said, make sure the drives are all green before replacing any of them.
Its not just the risk of making a mistake.
if you have single disk redundancy, then if a drive fails while your disk pack is rebuilding - you would loose all of your data.
Dual disk redundancy will allow one of the “old” drives to fail - while the pack is rebuilding onto a new drive, and still complete successfully.
I have it on Dual disk redundancy thanks so much!