Will drobo ask for bigger drive, even when at max volume size?

Hi there - curious if anyone knows the answer to this. Can’t find it in the manual.

When you run low on space, Drobo lights up the smallest drive and tells you to replace it with a bigger one (amber indicator). Let’s say you do this until you’re at the max volume size (64 tb for a 810n, 32 tb for a 800fs). When you eventually run low on space, is it still going to ask you to replace the smallest drive (amber indicator) even though you’re not going to get any more capacity by doing it?

I’m asking because I’m getting near capacity and I’m worried about forever being stuck with an amber indicator which looks very close to a red one at a glance - hoping that once no more space can be added, the lights stay green unless there is a correctable problem.

If you have set your max volume size on your Drobo to any figure (eg 24TB as an example) and you add additional HDD capacity (whether responding to amber lights or not) that increases that potential volume beyond that setting, your Drobo will automatically create another volume of the same potential size - and when you subsequently install larger capacity HDDs, any additional capacity will be added to support that second volume only. This means your first volume will remain as 24TB (as the example) and another potential 24TB volume will be created. Initially however, it will only have a small actual capacity as it is accessing the ‘extra-over’ from the HDD added to the array that triggered its creation. The second volume will appear as a second drive on your PC/Mac as well. This is known as ‘thin-provisioning’.

Hi TwinTigrer, I’m aware of thin provisioning - but Drobo also has a volume size limit. 32 TB on my B800fs and 64 TB on my B810n.

What I want to know is that if I have provisioned volumes that hit the max volume limit will the Drobo continue to bug me to replace my smallest drive with a larger one when doing so will not result in any additional capacity since there is no getting past the max volume limit.

The instruction manual doesn’t cover this scenario and I’d like to find out the answer before wasting funds to upgrade drives that result in no tangible benefit.


Every time a volume reaches 85% your Drobo will prompt you (amber light) to upgrade the lowest capacity HDD in that volume.
If you have multiple volumes on your Drobo you can manage that by moving data between them to keep under the 85% capacity.
Volumes can accept data beyond 85% but you will notice a degradation in speed when it hits 90%+ as it tries to find space within the volume for replication.
If you add a larger HDD that extends the capacity beyond the potential volume size your Drobo will automatically create a new volume for you.

Thanks TwinTiger - let’s take that answer one more step further! :slight_smile:

I have a B800fs. I fill it with 6 TB drives, so it has 2x 16 TB volumes with dual drive redundancy. I’m at the 32 TB storage limit.

If I then fill it past 85% will I get an amber light on one of my 6 TB drives? I’m asking because replacing it with a bigger drive won’t do anything because I’m at the 32 TB limit. You can’t have 3 volumes, only 2x 16 TB volumes, max - so I’m trying to figure out what happens.

I’m tempted to just buy another drive and see, but it’s a shame to blow $200 if it doesn’t really do anything.

Filling a volume on your current twin array past the 85% capacity will trigger at least 1 amber light.

The next part assumes multiple volumes can exist across HDDs - which I think it the crux of your question. I haven’t found anything that refutes this assumption, as volumes are effectively made up of HDD partitions (as a simplified comment) so it is possible.

If your volume limit on your Drobo is set to only 16TB and assuming your firmware is up to date, after seeing an amber light, adding a larger HDD initially will not increase your available space. It will allocate the extra-over space as “reserved for expansion”, and you will then see another amber light on another drive and a request for a second larger HDD which (as you have dual redundancy) yet again will allocate the extra-over space as expansion space and a third drive will then go amber. In theory, by adding a third larger HDD it should trigger the request for the creation of a third dual redundancy 16TB volume from the expansion space on the 3 HDDs - Drobo asks to do this via the Dashboard.

Under your common 6TB HDD + Dual redundancy arrangement, you will therefore need a minimum of 3 larger HDDs (and a fair but of time - factor in 24 hours for each drive replication) to be able to benefit from an increased HDD capacity.

Before you attempt anything, ensure you have an external backup copy of all your important data. It amazes me how many people forget or are unaware that a Drobo (or any RAID machine for that matter) is a single point of failure for their data. Also be aware to avoid SMR drives though I’m not aware that they yet come in sizes larger than 6TB.

Thanks TwinTiger -

I think we’re getting there. In my case, my B800fs is currently loaded with 8,6,8,6,6,8,4,8 TB drives. According to drobo dash, I have 33.81 TB of space. I believe that this is using hard drive manufacturer math, so it’s really about 93% of that which is 31.44 TB… I’m guessing that this is why I’m getting the amber light. If I swap the 4TB drive for a 6 TB drive, that should push me over 32 TB… which should mean I’m maxxed out. I’m hoping that means no more amber light - I just find it annoying… but it’ll be a $200 gamble to find out.

The $200 question is: were the Drobo software engineers smart enough to think of the edge case conditions. If they did, there should be no more amber light once you hit the max theoretical storage capacity for the device because you can’t fix the amber condition. In other words, once you’re at max - adding bigger drives doesn’t give you more space so you’re still at 85%+ capacity… so it would be nice if the device was smart enough not to bug you about it.

The reason I’m sticking with 32 is because Drobo states that the B800fs has a 32 TB storage limit which is done through two 16 TB volumes. Supposedly, there is no going bigger than the storage limit or the volume limit which means no 3rd volume. See:

Keep in mind the B800fs is a NAS, so the whole thing is done through thin provision - I don’t get to select the volume size. It automatically creates them at 16 TB.

I tried contacting support but they just quoted me the capacity limit on that page - which I really knew. They didn’t actually try to answer the actual question.