Very slow speed

I bought a Drobo 3rd Gen with a WD Red 6TB, my speeds are in the 1 Mbps range. I filled it in two weeks with 2.6 TB of data, but now its too slow to even copy the files back to another drive (imagine moving 2 TB over the internet…). The unit is directly connected to the computer via USB 3.0, with the latest firmware. I’m on OS X and Disk Utility shows no signs of file system corruption. I’m currently awaiting customer support but would be happy to hear back from the community. Is it a common problem? Thank you in advance.

There are a few ways to test or do a benchmark speed test on the unit.

Since you are on OSX, i suggest you can download a free copy of this mac app called “BlackMagic Disk Speed Test” from the Mac App Store. This will be able to run a speed test on the Drobo Gen3.

Typically you should see around 80 - 100 MBps (mileage varies…)

If you are copying say iPhotos or iTunes library file into the Drobo … and you are getting very slow speed… please don’t be alarm if I tell you is normal. Cos’ iTunes library has tons of small files in them and transferring of thousands and thousand of small size files will not get a all faster… Bottomline… DB or library file copy suffers from slow speed for any Disk Array…

A better layman test will be copying a single Large file say a .mkv movie file of 4GB or 8GB … even an ISO file of 4GB will do… copy this to the Drobo Gen3… and see the average transfer rate from the Finder … it will give you a rough speed test.

A single 4GB file copy to Drobo and tons of small files adding up to 4GB copy to Drobo. Single file copy speed will be very GODD but the later … suffers slow transfer speed.

Hi Don, thank you for taking the time for reading and answering my message. The speeds I’m reporting come indeed from the software you said. I also used another software from AJA just to be sure. My other 5400 rpm drives connected via USB 3.0 and USB 2.0 benchmark just as you say in Blackmagic, but Drobo doesn’t. Actually the tests are done on a fresh copy of OS X, the Drobo directly connected to the computer, no other peripheal on the USB ports connected (apart of the Apple keyboard), Spotlight indexing completely disabled, no other I/O operations done on the unit, no other software running, fresh WD Red drive full of data (it will take weeks to copy over to another disk…).

hi just a thought…
if your drobo is new - and you recently just populated it with tbs of data, then there is also a bit of a (settling period) where the drobo kind of sorts out or optimises the data. (especially if some data was moved off, it also spends time reclaiming the free blocks)

this may result in the slower speeds and you might be able to feel or hear the chatter of drives even if you are not doing anything. im not sure exactly how long it may need to settle, but i seem to remember a day or 2 for a gen1 4tb? (but if you do try to gently touch the drives to feel for vibrations, try to discharge any static etc first to play safe)

Hi giank,

Currently … how many drives are there in the Drobo Gen3?? ONLY one single 6TB WD RED when benchmarking speed is done??

Just wondering… cos’ Drobo best work with at least 2 drives (Default Single Disk Redundancy) or at least 3 drives if you turned on Dual Disk Redundancy.

that’s a good point don, i think that it mirrors the data onto the same drive as a backup and cross verifying on the same drive could potentially halve the speed.

thinking back now, i think it was docchris who mentioned to me that my SDR gen1 or SDR gen2 would be best with 2 drives, and that i should only add a 3rd and a 4th when needed.

For all Drobo such as Gen2, Gen3 or 5N, 5D … essential you need minimum 2 HDD for BeyondRAID to work.

Due to the “dynamic” nature of BeyondRAID… when you only have 2 HDD inserted. Drobo is basically working on “Mirror” Mode… but once you insert the 3rd or 4th HDD … BeyondRAID will auto configure itself and expand the disk space and still protects you from Single HDD failure… Is like from “Mirror” to “RAID 5” automatically without having to re-setup the RAID SET etc…

But giank case is strange … even if is only 2 HDDs inserted into a Gen3 … it should be that slow till 1Mbps???

I only see that such speed if ONLY you are copying thousands of small size files from PC/MAC to the Gen3. These small size files are usually small in the range of say less than few hundreds of KB. Such copy operation is extremely slow.

I added another 6 TB hard drive (now my Dropbo 3rd gen unit has two drives instead of one).

Had a good speed with Blackmagic (in the 50-80 Mbps range) until I filled it up (now the benchmarks are in the 2-5 Mbps range). It now has 2% of free space and the Blackmagic benchmark reports slow speeds again. My hypothesis are:

  1. After a very big data transfer to the Drobo, it needs to reshuffle data to optimize it for a few day, hence the slow speeds.
  2. If you fill it up over 90%, the Drobo hasn’t enough space to operate efficiently, hence the slow speeds.
    Those two possibilities could even be both true.

I tested the two drives independently and both have a 100 Mbps range of performance. Also after formatting the Drobo, I had pseudo native performance ranges even with only one drive.

hi i think your 1 and 2 are true.

drobo “can” slow down to do optimising / data shuffling / empty block reclamation
drobo “does” slow down as it gets full, especially at the 95% full mark, to try and help prevent or slowdown overfilling.

Oh… so the initial slow speed of the Gen3 was due to unit only has one drive… no wonder. :slight_smile:

With 2 drives - at 50-80Mbps??? I think the BlackMagic is reporting 80MBs (Mega Bytes) and not Mbps (Mega Bits). :slight_smile:

Thats sounds normal… but can be a little faster for Gen3 on USB 3.0 with full 5 drives.

Yes, indeed… if any Drobo has less than 10% free disk space… the performance is slow. That is why I always keep an eye on my Drobo to be less than 80% full.