Why did drobo changed from 1 drive to 2 drive for single drive redundancy?


I remember when I was using single drive redundancy it only needed a single drive. Now it highlights one of my drives saying I need two.

Can anyone please tell me why that is and how to fix it? I don’t have enough space to free up another HDD completely.


Can you post a screenshot, or the exact language that dashboard is using.

It never asks for two? it may ask you to add another drive if you are running low on free space, but that isnt related to your redundancy.

Thanks, here it is:

Before when I set it up years ago it said only 1 of my drive was gonna be used for redundancy but now it claims 2 is needed for single drive redundancy.

Could it be that your drobo unit has only one HDD inserted or maybe other drives are not properly inserted and therefore not connected?

I just checked but they are all firm. All lights are green except 1 red.

There has been no change in redundancy behavior. You need two disks in Single Disk Redundancy mode, and three disks in Dual Disk Redundancy mode.

i.e. in SDR, if you have at least 2 disks, you can lose one and still have access to your data; in DDR, if you have at least 3 disks, you can lose two and still have access to your data.

I think the language in Dashboard may have changed, but it is communicating the same information.

You can use a single disk - the data will be stored twice on the disk.

But isn’t only 1 disk is reserved for redundancy when using SDR? That’s what I thought.

Also guys I didn’t copy anything to this drive for like a year but the messages and the red light started showing recently which actually made me think the drive has failed.

So something weird is going on.


I think you are misreading the message.

It is not asking for two disks to store the redundancy data on!

It says “at least two disk for single drive redundancy”. which is exactly correct… you do need at least two disks for drobo’s single drive redundancy: one for the data & one for the redundancy - that adds up to make two disks! THAT is what the message is saying, it does only need one disk to store the redundant data on… but it also needs a disk for the actual data… you are correct, and so is the message.

if this has suddenly popped up then you need to contact support and send them your logs, and it would seem it is having an issue where it thinks it doesnt have enough disks.

Thanks I now see what you mean. Yeah it’s confusing and I am not a native speaker and it’s definitely a recent thing. I will contact support.