Drobo S capacity questions

Hello, everyone.

When I first set up the S I created three volumes of 2TB each. Subsequently, I have swapped drives and increased total capacity from 6TB to 13TB. I’m using one of the three volumes to store photo files. It is nearing the 2TB original allowance (as shown in Finder - I’m on an iMac), yet reviewing the total Drobo S capacity via Dashboard it shows 5.43 TB available for data.

The question is: Am I able to access that space despite the fact that the computer is reading that volume as near full?

In order to increase that volume, do I need to copy off the totality of data from all three volumes, reformat the Drobo to recognize the larger (desired) volumes, then copy everything back?

Is there a solution to this problem?

My downloads to the Drobo have slowed tremendously and I suspect it’s because the iMac is reading it as almost full with no accessible space.

Any suggestions?


hi, is it possible to post back with some more info about your drives, sizes, and status of dashboard/lights?
also do you know if you are using SDR or DDR (single/dual) drive redundancy?

for the volume size, i believe once you select a max size per volume, it can not be changed (without backing up and reformatting etc) but if you have some more info it would be useful when you can


Thanks (I just saw your reply).

It’s a Drobo S with Dual Drive Redundancy. I currently have one 4TB drive, one 3TB, and three 2TB drives. As of this afternoon, I am swapping two of the 2TB drives for 4TB drives.

Initially, as I mentioned, I set up three 2TB partitions thinking when would I ever generate more than 2TB of photos…

Downloads into the photo partition (currently at 1.9TB full) are painfully slow. I have no idea whether or not Drobo is “smart” enough to know there enough extra space or whether I need to offload everything, reformat, then upload everything again.

The dashboard tells me everything is working well and that there’s sufficient space (before added the new 4TB drives). Status light are green and happy. Drives are quarterly checked with Disk Warrior. All reports are good.

Drobo corporate support is woeful if you choose not to pay for ongoing support. I just need a clear answer before I decide to spend the next week shuttling files back and forth.

Any suggestions you have are appreciated.


hi thanks for more info,

for the volumes, drobo should always know how much data it has (used and capacity)
but your computer would see the current 2tb as max limit.
i am not sure if there are any mac-specific processes (or programs) that cause slow downs that badly though.

(i have heard about raid-like arrays of any make, getting slower when they fill up, but i have experienced low space in the form of just a few megabytes of free space :smiley: , many a time, on windows xp or older, and never experienced noticable slowdowns)

for the drive upgrades:
while i think you might be able to remove 2 drives due to ddr, i would suggest that you only upgrade 1 at a time.
eg basic process would be this:

step 0 (ideally you have a backup of all your data too)
(ideally the new/upgrade drive is of the same model/make as an existing 4tb drive it will probably work fine, though if it is not, then usual drobo recommendations are to upgrade firmware and dashboard first, followed by a full reboot of computer and drobo to make sure all is still fine).

then, to keep drobo on, and to remove one of the smaller 2tb drives (eg a 2tb drive) and possibly drobo is indicating one of them as solid yellow or solid red.
dashboard will probably update itself shortly after as it recognises a drive missing.
to then plug in the new/empty 4tb drive and to let it rebuild the data structures including on the new drive.
(it usually takes about 1 day per 1tb of data that you have).

HOWEVER - from re-reading your post above, it sounds as though your drobo itself, still has lots of space on it.
could you please help clarify how many of the blue led lights are lit up? and maybe you have a screenshot handy of the dashboard? (you can mask your serial number to play safe though)

and can i please ask if your other 2 volumes are empty?
(it may just be that if you were to move say 25% of data from one of the volumes, to an empty one, and then see after some time if it speeds things up for you, then its likely to be a mac progess. but please if you move, do this as a CPV method, eg Copy, Paste and then Verify your data before deleting anything.

Here’s a more frustrating problem:

I just swapped in the first 4TB drive. Drobo recognized that it’s a new drive and asked to format it. I’m using HFS+ but it’s telling me the drive max capacity is 2TB. It’s not giving me an option for anything larger.

While doing this, I figured I’d configure it for a 4TB volume, copy all the photos to it, then add the second 4TB drive and use it as a 4TB drive, too. This would eliminate the need to reformat the entire drive stack.

But despite the fact that HFS+ on an iMac running OS X 10.10.1, I can’t find a way to create a larger volume.

THIS is my new problem.


I’m not familiar with the Drobo S (I have the network attached 5N, which has it’s own internal filesystem) but if my understanding of the older directly attached Drobos is correct, doesn’t it go something like this:

You replace a 2 TB drive with a 4 TB, which adds to your overall storage pool. From that pool you have already allocated space for three 2 TB volumes. Now you have a bigger storage pool, isn’t it simply a case of creating a new bigger volume in the Drobo Dashboard, then formatting it using the appropriate tool on your computer (Disk Utility for OS X HFS+, Storage Manager for Windows NTFS); then copying your files from the older volumes to the new; then, once you’re happy with their integrity, deleting the old volumes and returning their space to the storage pool, from which you then create other, larger volumes? Or have I missed something?

That may very well be the best way to go. I struggle with making a correct choice because despite the fact that I have the photos backed up on external drives, the enormity of the task of copying and recopying 180,000 image files takes a crapload of time.

The Drobo is at my office and I will look into your suggestion this afternoon.

Thanks. Sometimes being too close to something clouds the issue. My biggest problem when inserting the new 4TB drive was not being provided with a choice of volume size prior to formatting. As a result, I have limited confidence that I will be given that option following the steps you outlined.

If I don’t, I’ll be back with an update and hopefully some new suggestions from the forum.

While the Drobo itself has not given me any reason for concern in all the time I’ve owned it, the piss-poor customer support model they employ leaves me feeling that I’ll abandon the brand if/when the S dies for good.

It’s too bad. I like the device.


I think the fact that you initially created three 2 TB volumes means exactly that. They are not going to expand as you add more capacity to the device and it would be rather disturbing if they did. However, you have unused space at your disposal - think of it as an as-yet unused partition on a single large hard disk. It’s there for you to use.

As I said, I don’t have a Drobo S and my 5N works a little differently, but I’ve no doubt that Paul will look in on this thread again and he has a lot of experience of the directly attached Drobos. My question for him is “does the Drobo S support thin provisioning and, if so, why would it seem like a good idea to create such small (2 TB) volumes?”

File copying does take a long time but fortunately it’s something you can set going and then get on with your life as it doesn’t need a great deal of user interaction if you plan it right.

The comment about customer support was a little unexpected as everyone here is trying their best to help you but, to be fair, I’ve seen it before and it does sometimes make you feel better to have a bit of a rant and get things off your chest. I know I appear a bit grumpy sometimes! In the absence of official support this forum is the only alternative so if you take a little time to formulate your question, giving as much relevant information as possible, you’ll hopefully get a helpful response. At the moment, I’m not really sure I understand what your problem is.

hi yup i try to read each new post on the whole boards and sometimes i miss a post or two.
(though am sure everyone wouldnt mind missing a post or two if it was spam etc) :slight_smile:

i think the key concept is from my first reply which just to paste it here is this:
“for the volume size, i believe once you select a max size per volume, it can not be changed (without backing up and reformatting etc)”

what might be a bit confusing (and it is something that doccrhis helped me to understand when i first got my 1st drobo), :slight_smile: is that all hard drives that we put into it, (either into an empty slot, or from upgrading a smaller drive into a bigger), simply all get added to the drobos total RAW capacity.

the raw capacity (using whole numbers for simplicity, such as in TB), is then used to capculate your actual USABLE space for data. This is based upon SDR or (DDR) protection, which subtracts 1 (or 2) of your largest hard drive sizes, and then the filesystem formatting eats up a little bit of space, which is why i usually take the remaining USABLE capacity and multiply it by 0.9

This ends up with the ACTUAL drobo capacity which is usable for data, and this is where the max volume size comes into play. So if (for example) the ACTUAL usable space was 3tb, and your max volume size that you selected was 2tb, then all volumes will only show themselves to the operating system as 2tb, and you would have 2 volumes (showing 2tb free space each) but you would only be able to utilise 3tb of data across them, eg 2tb in the 1st, and 1tb in the 2nd, or something proportionally similar).

so if i use one of my own gen1 experiences as an example, then what this essentially means, is that when i had 4x 1tb drives, and when i upgraded 1 of them from 1tb into 1.5tb, i “did not” actually gain any usable space :slight_smile: it might have taken a 2nd post or email from docchris back then for me to understand, as the initial expectation was that my usable space would jump up by half a tb :slight_smile:

this was my experience with DAS models, (as i think some NAS models have variable settings but only get a NAS model if you really need it, i like the das ones) but i hope this helps a bit, but please feel free to ask more quesitons if you need.

for johns question about volume size, please find some more info below for you john:
i have posted a fair few times in the past about this (and hopefully i wont forget one of the pros) :slight_smile: but there are always pros and cons about having smaller max volume sizes, and ultimately its down to each user as to their preference, though for me, the main pros are these:

  • easier for me to manage, and sync for backups etc
  • works with XP (some computers or devices can only read 2tb max per volume)
  • quicker chkdsks per volume (eg if computer crashes, i run a chkdsk on all volumes but one at a time, some take time but this way i can run some inbetween other actions, and can also set some to run overnight etc)
  • quicker full virus scans per volume (similar)
  • quicker full content indexing via “cathy” by r vasicek (a great windows tool)
  • quicker boot times reported by other users (rather than having 1 huge 16tb volume)

and only downside for me is that each volume eats up a drive letter, but there are still plenty available :slight_smile:

Ok, thanks Paul. Interesting that your preference is for directly attached devices while mine is for NASes.

Before I go on with anything, I would very much like to thank johnm and Paul for your thoughtful replies.

I hope I haven’t come off as ungrateful. My mini-rant about Drobo support refers to the fact that I tried to get a simple question answered and they kindly asked me to pay for the privilege.

And so maybe it is my question that has caused some of the confusion regarding my confusion with my Drobo S. Please let me try again.

I now have the following installed:
two 4TB drives
one 3TB drive
two 2TB drives
for a total of 13.64TB useable drive space
6.34TB is for data, 1.81TB for expansion, 5.47TB for protection, and 11.14GB for overhead.

I started with three named volumes (essentially DROBO1, DROBO2, DROBO3) each of 2TB.

I now want to create a new volume of larger capacity (3 or 4TB) so that I can copy all 1.98TB of photos to the larger volume. Currently, photo downloads take HOURS and I assume this is the result of virtually no available disk space on the photo volume (DROBI1).

I have an additional 4TB drive I’d like to install, but since the protection cycle is upwards of 31 hours I don’t want to do anything during that cycle (rightly or wrongly.)

So, (what I perceive to be an) easy question: Can I create a volume larger than 2TB? When installing the first of the 4TB drives earlier this week, I was not given ANY option to select volume size. It essentially told me the new volume would be 2TB. So what I now have are four 2TB volumes.

I wasn’t under the assumption (even if it appeared so) that I could increase the size of an existing volume. I simply wanted to add enough new drive capacity to create one new 4TB drive so I could port the photos and continue on my merry way of dumping in about 800 new images a week. (No, we won’t get into my lack of desire to just delete mass quantities of images as I go… We’ll let my shrink or wife handle that.)

Has this reframed my situation enough to get a definitive yes or no? I’d love to know before I install the next drive and be told I can only have another 2TB volume.

Again, your comments and suggestions ARE appreciated and useful.


Well, according to this article you should be able to create a volume of size 1, 2, 4, 8 or 16 TB through thin provisioning even though you don’t have that amount of space available. However, reading between the lines (it isn’t at all clear from what’s written), that may only apply if you take the option to maintain a single volume. You chose on original setup not to take that option - opting for three 2 TB volumes instead - so it appears you might be stuck with using only 2 TB volumes in future, unless you reformat and start again. As I said, I don’t have any practical experience of the directly attached devices though others here certainly do, and that’s just my interpretation of what that article says in the light of your comments. I’ve read it over several times - what do you make of it?

That said, thin provisioning is clearly working on your device to give your four 2 TB volumes from only 6.34 TB of available storage space. I put your five drive sizes (4, 4, 3, 2, 2) into the capacity calculator (using 5D/5N as there is no option for the S) and it’s clear from your figures that you have dual disk redundancy enabled. You have a lot of capacity (1.81 TB) tied up “for expansion” which will only be released into the “for data” pool when you substitute that extra 4 TB drive for one of the 2 TB ones. Try it in the calculator - your “available for data” figure goes up to 8.17 TB.

So it seems you may have a choice to make (always assuming my interpretation is correct, so by all means seek a second opinion). Either continue to add 2 TB volumes as your capacity grows, or start afresh with one single 16 TB volume or two 8 TBs or four 4 TBs. Personally, I would always go for a single block of storage with meaningfully named top level folders in the root - but then, I favour network storage which allows multiple shares from within that single volume.

What, on the face of it, seems like a simple question is actually really quite complex.

its nice healthy discussion :slight_smile:
sometimes i get carried away and post a lot of info though, which might make my answer harder to find, so ill paste it in again here for you:

i think the key concept is from my first reply which just to paste it here is this:
“for the volume size, i believe once you select a max size per volume, it can not be changed (without backing up and reformatting etc)”

answer for your current case = no, i dont believe you can modify your originally-selected volume sizes, unless you backup the data somewhere else, and reformat the drobo from scratch.

Other questions:
im just wondering something as well…
if you have another drobo volume which is empty
(and when your drobo is not rebuilding)
and if you have enough usable free space via dashboard,
what happens if you try to copy and paste say 1gb of photos from where you did, but this time pasting it into the other volume which is empty?

(this is just to see whether the programs you are using, speed up at all, if the destination volume is hardly used)[hr]
For Drobo Devs:
suggestion would be to add a list of pros and cons on the initial volume creation steps, to help to inform users a bit more.
(i forgot if its there already, but if not, maybe would be good to mention that once a volume size is selected, it can only be changed via backing up and reformatting etc) - even if brings up a popup window or something as an extra step, its probably not a bad idea :slight_smile:

Well, I’m glad we agree Paul. You knew it from experience and I managed to work it out for myself. But I don’t think it’s the answer Dave was hoping for!

CORRECT!!! But thank you both. I had read Article ID AA-01405 but had hoped for a work-around that might have been introduced via subsequent firmware updates.

I am now at the point where I’m either going to live with the situation and a never-ending stream of 2TB volumes, or bite the bullet and copy the entire contents of the Drobo to yet another drive, reformat, then recopy. I’m just tired of shelling out more and more money for disk space… (sigh)

If the device will let me use thin provisioning once I install the next 4TB device, that would “solve” my problems and only require (yet) another BAD (big-ass drive) to allow me to dump the photos to a larger-than-2TB volume. Since it’s taken years to fill a 2TB, I can probably happily live with a 4TB volume. If I exceed 400,000 images, I have bigger problems to attend to…

Once again, I appreciate your thoughtful, well-written replies. Problem (maybe) not solved, but certainly addressed and uncertainty removed.


P.S. Anyone know why I don’t get e-mail notifications even though I click on the “Subscribe and receive email notification of new replies” button under Thread Subscription?

cool, were happy to provide you with music, just sometimes it might not be in perfect tune… :slight_smile:
and to quote a famous film, when you asked it to change volume sizes on the fly, the drobo was saying - “i’m sorry dave, i cant do that” :smiley:

for the email notifications, maybe you could recheck your email address from profile settings, just in case, and to see if any emails went to a spam folder? (as i reply to lots of threads and posts, i often get several email notification in quick succession and sometimes the filters block it for me too but i then find it in that folder, usually.)

sometimes it seems that our perceived data usage, is a bit like the majority of Moores Law, in that we end up filling up the drive more more quickly then we thought…so i think there will always be a limit being reached by all at some point.

btw there is one tool that Bhiga has successfully used, called DriveBender, and i think he used it to merge not volumes, but i think multiple drobos into 1 huge storage pool - BUT i dont know enough about it to recommend, and it would certainly add an extra layer or 2 of complexity to both the setup, (and recovery) should anything go wrong.

one question i had for you, is do you simpy store your images on the drobo, and just open some up when needed to view, or do you actually use any special programs which process them or catalogue them etc, such as adobe programs?
and a 2nd question (sorry) :slight_smile: is if you have any indexing services running in the mac?

Again, a general and hardy “thanks”.

As to e-mail notifications - checked and rechecked. No go. Such is life…

Drive Bender is a Windows-only tool. I’m running a Mac. But thanks for the lead. May be useful in other parts of my life.

So, I dropped in the second new 4TB drive, and lo and behold, I was offered a chance to create a new 2TB volume. Seems like I’m going to be forced to offload everything onto a BAD, reformat, then reload.

To be honest, this whole setup is used by my father. He’s as useful with a computer as I am able to make him. My hopes for establishing one megadrive on which to hold ALL of his 185,000+ and growing digital images was to simplify the download process for him. Even changing the destination drive can mess him up and cause him to “lose” pictures. (Which I must then “find”.)

Lightroom does a marvelous job of managing digital files, but he’s 81 and while he moves like he’s 65, he claims his head is full and I want to simplify, not complicate, his use of technology. He’s adept enough with the software that he can work at the machine for hours at a clip, but I’m not looking to move his keys on him while he’s sleeping…

So, ultimately, this simply requires throwing money and time at the problem and it will be resolved. At least it’s just my time…


P.S. I do believe that I set up indexing on the Mac. How might that impact stuff?

ah if you find another use for drive bender for you please feel free to post back,

thats cool that you set up something for your dad, and that he’s using it for his photos.
you might already have this in place, though just to mention it for safety that its probably a good idea for you to help him make a backup of his photos, just so that ALL his lifelong images are not (only) on 1 device, regardless of what type of device, just because another thing that can help people to lose stuff, is by deleting a root folder and saying “yes” by mistake.

while it might not be the easiest of processes to do, you might find use for a tool called Quickpar which does actually work on the mac this time :slight_smile: which can take a bunch of files (or photos) in a folder, and can recreate n-number of missing photos simply using the remaining ones, just in case a photo gets deleted by mistake. just fyi.

(for the indexing, i think the only main impact that if could have, is a bit of slowdown on some operations, and possible file/folder/device locking, probably on a temporary basis, depending on how often it is scheduled to run, and how “deep” the scan is.)