Space Issues


I’m worried that I know the answer to this but here goes…

I have a Drobo V1 with 4 x 1.5TB drives atached.

When I initially setup the drobo it was connected to my iMac directly with USB. During the build I was not allowed to create on big Volume and had to create 2TB max volumes as that was a USB limit (apparently). This I did and I started off with 2 2TB volumes and have ended up with 3 since I upgraded to the 1.5Tb drives.

One volume is used for TV stuff, one for movies and the other for odds and sods. I’ve been getting a lot of finder 51 errors lately which may or may not be related but it has highlighted that the volume with the TV shows on has only 30Gb free from the 2.2Tb volume.

Now I know that the drobo manages the storage itself and that the volume info should be ignored but I would guess that this is not the case once you get to the top end of that space as the OS will see that the filesystem is full and act accordingly.

So I guess my question is

What happens to a filesystem that hits the 2Tb volume size limit ?
Is there any way to expand it ?

I think this will be a nightmare no matter what the answer is but if I can ask that you giggle in quiet at least :slight_smile:

Im not sure what you mean by this? a volume is a volume, if you have a 2tb volume and you try and put 2.1 TB on it - your OS will say out of space, just like on any other 2Tb disk?

Not sure where you got the USB limit thing from, there’s no such limit that I’m aware of - my Drobo is on Windows, but it’s 5 TB. Drobo Dashboard should have given you options and a slider to define the maximum volume size.

Whatever your defined volume size is (in your case, 2TB), then that’s what Drobo does, “chunking” the available storage into defined volume sizes.

If you want to change the volume size limit, you’ll need to back up your data elsewhere, reformat with Drobo Dashboard to the maximum volume size you desire, then copy your data back. I strongly suggest you keep your backup medium as a backup too, because backups are good to have.

I thought the USB limit sounded odd, but I’m a PC Guy and thought maybe it was something Mac specific so didn’t query it

The 2Tb limit is not a mac thing and may now potentially not exist anymore but when I created the volumes on the drobo I was limited to 2Tb.

Google “2TB limit usb” and you’ll see what I mean.

“volume is a volume” - what about zfs ? volumes will expand dependant on space in the volume pool.

I think you’re right about the filling up bit which is unfortunate as I was hoping that he drobo may have done some flash remapping at the back end. It has to remap at the back end to handle where the data is stored already given that I have 3 2Tb volumes and only 4.1Tb of physical space. It’s not just going to allocate the first 2Tb to the first volume and the next 2Tb to the second and only 100Gb to the third.

So given that it doesn’t do that it must keep a physical to logical mapping of the data. Then it should be able to reference the physical data no matter how much space the volume is saying that it’s used. The only real stumbling block is the OS and referencing the logical blocks as the kernel will probably allocate memory to handle the file system and it probably can’t cope with it being dynamic in that way.

Sorry - rambling a bit. Basically I’m screwed - I think that’s the jist.

Oh well - I’ve been wanting to move 3.5Tb of data around for a while :frowning:



i think you would find on zfs - you still shouldnt “Ignore the volume info” as you put it???

i did google 2tb limit usb and could find NOTHING - the closest thing was some guy on a toms hardware forum who said that there was a limit - closely followed by someone smacking him down and pointing out thats an XP limit and not a usb limit.

i had a first gen drobo, as soon as they were available, plugged into vista over USB, and i have never had any kind of limit. i think you will find it was an OS limit (XP couldnt support more than 2TB volumes), not a usb limit.

For the sake of my sanity, I’m obviously not on my own when it comes to the usb limit question.


is a mac world review of the drobo which states

I assume that it would have taken that from the manual. I think that this may have been a firmware issue on the drobo rather than a generic USB one as I see the following comments on www.computeraudiophile.com

[quote]“The Drobo user guide says that USB limits any single “pool” of data to 2 TB”

“Some threads on the Drobospace forums do say the 2 TB limit is fixed with a firmware update but nobody seems to have the 100% definitive answer.”[/quote]

Although I have looked for these I cannot find them on drobospace.

I didn’t get my drobo as soon as they came out but I was a fairly early adopter (mid 2008), but I would have thought that the limit wouldn’t have hit you anyway as the 1Tb drives would have been only just available when the drobo was released. Anything below 4 x 1Tb drives wouldn’t have created a volume above 2Tb so it may not have been apparent at the time.

Still - doesn’t change the fact that I’ll have to dump all the data and reformat (oh joy!!!) - now what’s that word that rhymes with rollocks :slight_smile:



my first drobo did indeed have 4 x 1tb :stuck_out_tongue:

im just about to pass 10TB of data on my pro… i cant imagine how i coped with having “only” 3Tb back then :slight_smile:

I think part of the confusion is that dashboard defaults to 2TB when you go to format and most customers do not notice that it’s a slider bar where you can move the bar down to 1TB or up to 16TB.

maybe there should be a drop-down menu? so that initially there is nothing - and they are forced to choose?

or radio buttons with nothing selected at first - and you can say that 2tb is the recommended?

basically have a menu where they HAVE to choose - there is no default already selected.