G-Drive to G-Speed Q data transfer is extremely slow


I am transferring data from G-Drive 4 and 2 TB USB 3 HDDs to G-Speed Q 32 TB USB 3 RAID 5 and I am getting speeds of about 23 MB per s instead of USB 3 speed of 625 MB per s. I am using the iMAC Pro with its two USB 3 input/outputs. All drives formatted at MacOS Extended (Journaled). A folder containing 32 large video files, total 1.69 TB took 20 hours to transfer to G-Speed. Why the transfer is so slow? iMac Pro is running the latest Mac OS 10.13.3. I have about 20 TB to transfer and it will take me a week at this snail pace. If I cannot correct this problem and the G-Speed Q stays at these very slow data transfer speeds I cannot use it to edit my videos and photographs. I need your help, please.


Test the Q separately with something like BlackMagic or AJA system test to see what its throughput is.

The transfer from the other G-Drives would likely be the slowdown point. Also USB3 devices don’t get 625MB/s that is the theatrical ceiling for the bus and is way beyond what the drives are capable of. You will likely see close to 350MB/s with your unit when it is from system to Q.


Thank you for your response. I installed Blackmagic and I am getting read speeds of 130MBps from The G-Drive and 170MBps write speed from G-Speed Q. My calculation show that if on the average I get 150MBps read/write my 1.68TB data should have been transferred in about 3.1 hours. It took 20 Hrs.

You said I should likely see 350MBps. I wonder why I am getting significantly slower speeds by a factor of two. This means both drives are running at about 1/4 the nominal speed of USB-3.

This test software running on the iMac Pro tests them separately. I wonder what may be the problem here. There is a bottle neck somewhere.

Could converting to Raid 5 can delay data transfers so much? I would appreciate your help and advice, please.


The thing is, the Q is a much older controller, it doesn’t operate at optimal speeds like our G-Speed Studio series or our newer G-RAID removables. RAID5 also slows down the performance. The # I gave you was based on RAID0 optimal speeds not 5.

The types of files also affect transfer rates, lots of small files take considerably longer than small amounts of large files for example.


I am getting about 7 times slower speed. Instead at transferring at about 150MBps it is transferring at about 20MBps.

How much Raid 5 could reduces transfer speeds, please? I doubt it could be 7 times slower? Also, I think Raid 5 Transfer is not an issue, because when I did the test Blackmagic was writing onto Q Raid 5 disk and the Raid 5 speed reduction must be included in its writing. So it cannot be Raid 5 slowing the data transfer. The time lost due to Raid 5 is already included in the test. Therefore, the question is what can slow the data transfer by a factor of 7, please? Could there be something else? Could you ask your engineers, please?

I have stopped my data transfers onto the 24TB Q until I understand this problem. I will appreciate your help.


20MB/s is very slow that is closer to USB 2.0 standard speeds. Are you sure you are attaching your Q to a USB 3.0 port? If you had access so another computer I would suggest trying it on another system entirely to see if its not something specific to your computer.

Other than that the only reason it would have a severe performance drop is due to a drive problem. If one of the drives is starting to fail it will bring the performance of the entire unit down considerably. However its not possible to tell which has failed unless it warns you when a full failure occurs and the light on its bay is red.


Thank you for responding. As I said before, I am using a new iMac Pro which has fast USB 3 ports at its back. Both drives are connected to these USB ports directly into two ports side by side at the back of the iMac Pro. They are supposed to be high speed as given on Apple web site.

I gave you my Blackmagic test results they are much higher than what I am getting when I actually do the transfer.

Last weekend I moved 6.83TB data on my Seagate Video drive to a new 10TB HGST NAS drive where both drives are internally connected into two drive slots on my old 2007 Mac Pro. It took a little over 11 hours for the transfer much faster than the 20 hours it took to transfer 1.69TB to the new Q drive using my new iMac Pro.

All the drives in the Q are 4 new identical model HGST Helium drives. If any is bad, I wonder why did I get a reasonable Blackmagic test results. If there is a bad drive in Q, how can I find it an replace it, please? Is there a G-Tech diagnostic tool to find out if all HDDs functioning normally or not, please?

I am building up this 24TB Q drive with my data to make it my main data disk for iMac Pro. If it keeps this very low data transfer rates I cannot use it. I need to solve this problem, please.


NOTE: I forgot to say that the data I am transferring are a small number of huge video files. Therefore, as you asked before, I am not transferring a large number of small files, which can slow down the data transfer.


The Q is an old product with an old controller. The max throughput on the 32TB model we made is roughly 250MB/s. The 350 I mentioned was a typo, We do not have a drive diagnostic tool other than a standard HGST or WD drive test tool but they won’t work via the enclosure since it forces them into a RAID.


Thank you very much for trying to help me. I really appreciate it.

If I can get 250MB/s I will be very happy. At the moment I am getting 23MB/s, 11 times slower.

Can I try the HGST test tool? Or do you mean they do not work with Raid 5? In this case if there is a drive that is slowing the data transfer then I can only find out when that drive completely fails, which is not good. It will be really better if there is a way for me to find out which drive is causing the problem. Could there be a third party software that can help, please?

If there is no way to find out with a diagnostic software, I thought it may be a good idea if I made some tests myself to try to figure out where the bottle neck is. I have another USB-3 Q raid 5 which needs setting up. Can I move the drives from this one to the other Q drive in same order and test it in the other Q drive, please? This will show me if the problem is with the drives, the enclosure or something else. I will hopefully work on it this weekend and let you know what I can find out.

NOTE: Since I used two different G-Drives, 2TB and 4 TB, to transfer the data from, which gave the same data transfer rate, I do not think the problem is there.


The only way to test the drives on an individual level to see which one might be under-performing is to remove them from the G-Speed Q and place them individually in another enclosure or dock and run a speed test on them or health check type of software. In the enclosure it keeps them all together as a RAID5 and so you can’t get individual readings.

And yes if the other G-Speed Q also has USB 3 then the controller will match and the drives can be swapped.


I get really slow USB 3 transfer speeds on my “Q” as well. Only around 40mb/sec vs 210mb/sec when it’s eSATA.