Maximum usable capacity 5N vs 5D


I was wondering what the reason is behind the limitation that the 5N has for the max usable capacity limit of 16TB, whereas the 5D has a max usable capacity of 32TB (according to Drobo’s own KB) and if it will become an issue with the 5N with larger and larger hard disks emerging.

Does the 5N really limit usable capacity of a pool to 16TB?

Example: If I buy the 5N and fill it with 2x 6TB drives (yes I know, officially not yet supported, but they do seem to work) and 3x 4TB drives, does it recognize it has 24TB of raw storage space or is it not possible to create a pool of that size? This is basically the only thing holding me back whipping out my credit card and throwing it at my screen :wink:

Or is the KB article out of date and does the 5N support larger pools like the 5D does?

Any insight into this is appreciated.

I’d like to reiterate this question as I’m interested as well. Earlier this year I dropped a hefty wad of cash on this device and am quite put out watching every other device get a capacity upgrade.

I have just put yesterday 2 hard drives 6 TB Western Digital RED for replacement of 2 4TB - I have exactly the config you describe : DROBO 5N - 6+6+4+4+4 = 24 (21,83 real) protection=5,49 extens=0 non allocated=317GB usable space=16,30 - as you can see, the 5N does not create a second volume of 16 T and now i lose 317 GB, waiting for a new firmware which can use these GB and accept more 6 TB drives.
The 6 TB works perfectly : firmware 3.1.1 (8.35.45) and Drobo Dashboard 2.5.4
I apologize for my english, I am french.

This is a bit odd, as the DroboFS used EXT3 (which has a volume limit of 16TB), but the Drobo 5N uses EXT4, which has a volume limit of 1EB (1 Exabyte - you don’t have to worry about this :slight_smile: ). Migrated disk packs from an FS will still be limited to a max volume size of 16TB, and the Drobo will just create a second volume (I have 5x4TB drives installed now, so the next upgrade I perform will add a second volume). However, the example of 6+6+4+4+4 on an 5N shouldn’t need a second volume on a 5N native disk pack, at least as far as the filesystem is concerned (which is why the KB article is very confusing for me - it might be written conservatively for those with FS migrated disk packs).

This issue also the only thing keeping me from buying a 5N. Any change the Drobo guys can shed light on this ?

Best regards
Jan Jessen

I have a brand new 5N and I would also like to know if I can use 5x 6TB WD Red NAS HDDs. Depending on how I set it up, I could max out at around 27 TB (factoring in the OS HDD capacity tax), and that would be sweet. Is it possible now and is the support website just out-of-date, or is it limited to the 16TB? Could this change based on a future firmware update?

I am with everyone on this thread. I would really like the 5N to be able to support the higher capacity. 5 x 6TB disks sounds real good to me.

It’s unfortunate that I thought the 5D and the 5N were cut from the same cloth when I bought the 5N, but obviously not.

I was planning to buy within the next 30 days but not if this question can’t be answered. I don’t want to get stuck with old technology. Has development stalled on this product because of a new product with built in cloud capability? I visited their booth at the PDN Photo Plus Expo and couldn’t get an answer about this issue there. The new cloud option looks nice but I really want to see if support for the 5N will continue.

It would be nice if someone from Drobo would reply.

This 16T limit came as a surprise to me, I pushed the 5N as a backup solution at my work place over other solutions mostly because of the 5 drive options and network capability, expecting it to last quite some time because I assumed (my bad) I could latter replace some 2GB drives with some much larger capacity ones later on.

Many if not most small/medium (profitable) firms make hardware buys late in fiscal year to try and deduct some expenses, guess what?6GB drives are already here and now is the right time to upgrade and will probably do to the possible extend of 5N but Drobo please take note: Already looking elsewhere for alternatives if another backup array is needed next year.

Yes, I too would like to be able to put 6TB drives in my 5N. It seems to be doing fine with five 4TB drives.

I would also like to know if the capacity relates to the totaled size of all five drives, or only of the usable capacity. For example: if I were to use five 6TB drives, and set for double redundancy, would the Drobo work at a max of 16TB, or would it not function correctly.

Seagate is now shipping 8 TB drives, and now after two Drobo 5N purchases I discover that there is a hard (for now?) 16 TB limit on the device… not good!

I am in the same boat, Caribou. I just bought a second one, and had planned on bumping up from 5 3tb drives to 5 6tb drives.

BTW, I heard the Seagate 8tb drives are REALLY slow, so I wouldn’t buy those at the moment or would only use them for backups or static data - not for active data like streaming recorded shows or movies.

I really hope Drobo announce something soon. I’m in the market for a 5 bay NAS and really like the look of the Drobo 5N. I’m very keen on putting in the new 8TB archive drives from Seagate as although they’re slower than normal drives, it’s still faster than gigabit ethernet anyway and I won’t be accessing the NAS 24/7. Until I hear that Drobo will be updating the 5N to support 8TB drives and max capacities far greater, I’ll hold off on my purchase or have to go elsewhere. The max capacity should be 48TB for both 5D and 5N as we’re going to see drives within a year that will max that out in a 5 bay system. My concern is that they’re planning on releasing new models to replace the 5D and 5N and leave current purchases SOL.

From what I’ve read, the WRITE speed may be somewhat slower, however the READ speed ought to be similar to other 5400 RPM disks. The “advertised” read/write speeds are on par with other large drives, however, so I’m hopeful they’ll work just fine in-practice especially for media that is rarely-written/mostly-read.

That is, if they are ever supported in the 5N.

Good to know, Caribou. I hope that they update the firmware this year.

I have five 3TB drives in one of my Drobos, calculated this to see how close I could get to 15.97TB:

My current setup:
3TB - 2.7284841053188 formatted
15TB - 13.642420526594 formatted
Drobo - 10.9139364212752 with redundancy

With a full stack of 6TB drives:
6TB - 5.45696821063758 formatted
30TB - 27.2848410531879 formatted
Drobo - 21.82787284255032 with redundancy (won’t show all of this until 5N firmware is updated)

If you have only one 6TB drive, it adds space based on the smaller drives for expansion and protection:
3TB - 2.7284841053188 formatted
3TB - 2.7284841053188 formatted
3TB - 2.7284841053188 formatted
3TB - 2.7284841053188 formatted
6TB - 5.4569682106376 formatted

Drobo - 16.3709046319128 formatted
Drobo - 10.9139364212752 with redundancy, 2.73 Reserved for Expansion, 2.73 protection

If you have two or more, it adds space for protection based on the larger drive, and zero reserved for expansion. In this case, three 6TB:
3TB - 2.7284841053188 formatted
3TB - 2.7284841053188 formatted
6TB - 5.4569682106376 formatted
6TB - 5.4569682106376 formatted
6TB - 5.4569682106376 formatted

Drobo - 21.8278728425504 formatted
Drobo - 16.3709046319128 with redundancy, 0 Reserved for Expansion, 5.46 protection

17,072,495,001.6 KB (15.97 TB in Win7)
17,578,125,000.0 KB (16.37 TB actual Drobo space)

Difference: 401.73 GB more than what Windows would report. This is as close as it would get, I believe, so I would expect that anything more than this would be wasting space until the firmware was updated.

I have 3 FS boxes and they are starting to look really lame now that 8tb drives are shipping.

“If your drive fails just buy a new and bigger one!” they said.

None of my drives have yet to fail… If Drobo Inc. wants any of my future money they better keep some promises. The 16TB limit is now very limiting, do some upgrades; like at least 2 peta or something.

How would you even achieve that with a 5-bay NAS? A quick look at the Drobo capacity calculator indicates that it would require 5x 500 TB disks. Yup, we’d need half-petabyte disks to get to a 2PB storage pool.

The SATA controller in the Drobos probably supports 500TB disks (if it does implement LBA48 correctly), but there is no way that this could be achieved with a current gen Drobo NAS.

If this graph [1] is any indication, HDD capacities increase an order of magnitude every five years. Going from our 5TB to 500TB disks would therefore require ten years. I sincerely wish Drobo to be wildly successful, and that they sell a ton of 5Ns, but I also hope that in ten years time they have a new, better model.

For starters, this new Drobo will require much more memory to manage a storage pool this large. Second, I hope to $DEITY that they include a faster network interface. Can you imagine what it would be like to backup 2PB of data over a 1 Gbps link? According to Google it is 208.5 days, or more than 6 months! That is assuming that you can actually sustain 1 Gbps transfers, i.e., you better not try to do anything else with that Drobo while it is backing up or restoring.

A much more reasonable number would be to increase for one order of magnitude, i.e., from the current 16TB to 160TB. This would give the 5N a nice five year product life, and the next model could come with a 10 Gbps interface, which would keep backup/restore times in line with the current offer (i.e., one order of magnitude larger storage, one order of magnitude larger bandwidth).


I would like to see them update the firmware too, 16TB max capacity is not acceptable. Even their Drobo with 4 drive bays has a capacity of 32TB. According to their website, it supports up to 6TB drives so the max raw capacity would be 24TB ( It can’t even hit it’s max capacity yet.

How can it be that a 4 drive bay chassis can have a max capacity greater than my 5 drive bay chassis?

I really like their product, but I am very unhappy about this capacity issue.

Drobo please shift it into gear and get us an update for higher capacity.

I specifically asked them about this.

Greater than 16TB support is definitely coming for the 5N, in the coming months.

According to the product description on the DROBO website, you can use it for up to 30TB. Can any one confirm this actually true.