Slow DNG copy on hard drive from C-Fast

Hello everybody,
I have some issues with RAW 4:1 DNG copies. I want to know if it's common.
I was shooting URSA mini Pro 4,6K 60fps.
I'm copying the data on a macbook touch bar from my transcend CFast reader, in USB 3, through a apple usb-c adaptor. I replaced this cable + adaptor and I used a cable in usb-c after my problems to see if it make a difference but it doesn't !
When I copy on internal drive everything is fine. The speed is maximal, around 250 mo/s, which is the max value I can have with Blackmagic speed test on a C-Fast with my reader.
Then when I copy on my hard drive 5To Lacie Porsche design, it start at 90 mo/s, which is the max speed I have with BM speed test, then after few minutes, it fall down between 30 and 15 mo/s. So it takes around three hours to copy my 235Go card...
I tried with different cables (usb A + adaptor / Usb-c / Through a calldigit thunderbolt 2 hub), and on a seagate 5to and another Lacie 8to. It always happen after few minutes ! Same thing when I copy from my internal macbook drive to the Lacie 5to...
I tried with some prores on the same card, in this case it keep the max speed during the all copies.

Is it because it's small 4 Mo DNG files that the hard drive saturate and the speed fall down ? Anyway, it's not acceptable on a set to get such low speed transfert. Somebody has an idea ?

Thanks guys !

Hello everybody,
I have some issues with RAW 4:1 DNG copies. I want to know if it's common.
I was shooting URSA mini Pro 4,6K 60fps.
I'm copying the data on a macbook touch bar from my transcend CFast reader, in USB 3, through a apple usb-c adaptor. I replaced this cable + adaptor and I used a cable in usb-c after my problems to see if it make a difference but it doesn't !
When I copy on internal drive everything is fine. The speed is maximal, around 250 mo/s, which is the max value I can have with Blackmagic speed test on a C-Fast with my reader.
Then when I copy on my hard drive 5To Lacie Porsche design, it start at 90 mo/s, which is the max speed I have with BM speed test, then after few minutes, it fall down between 30 and 15 mo/s. So it takes around three hours to copy my 235Go card...
I tried with different cables (usb A + adaptor / Usb-c / Through a calldigit thunderbolt 2 hub), and on a seagate 5to and another Lacie 8to. It always happen after few minutes ! Same thing when I copy from my internal macbook drive to the Lacie 5to...
I tried with some prores on the same card, in this case it keep the max speed during the all copies.

Is it because it's small 4 Mo DNG files that the hard drive saturate and the speed fall down ? Anyway, it's not acceptable on a set to get such low speed transfert. Somebody has an idea ?

Thanks guys !

Obviously Apple did genoan (i came from Genoa and can do joke about us).
If work fine from usb-c to internal (thunderbolt to pciexpress chipset) cannot work fine from to the same bus.
May be Apple used a not good chipset to manage data between usb-c thunderbolt port and when you go in and out in the same chipset it have trouble to manage datas. It’s the same if you check usb3 port of iMac, two port near monitor support are faster then other two in external position... but with the price of apple product I ask the lighting speed not cheap Cina chipset...
Also Mac Pro trash can have problem on thunderbolt, one only chipset to manage data, work at couple and when you attach a monitor to a thunderbolt the near port slow down transfer rate... absurd... it’s the reason be cause I ever tell that apple stop to produce computer when Jobs dye, and at today we can see only toys not professional computer like 10 years ago.

On a bad reader usb3.0 / hub 3.0 on a mobile workstation hp I reach from 80 to 160mb to transfer from sd to hdd mechanical. From ssd to mechanical i reach 200mb. I should do better if chipset allow you.

Probably a double copy give you faster result
From cf to ssd, from ssd to hdd external


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Obviously Apple did genoan (i came from Genoa and can do joke about us).
If work fine from usb-c to internal (thunderbolt to pciexpress chipset) cannot work fine from to the same bus.
May be Apple used a not good chipset to manage data between usb-c thunderbolt port and when you go in and out in the same chipset it have trouble to manage datas. It’s the same if you check usb3 port of iMac, two port near monitor support are faster then other two in external position... but with the price of apple product I ask the lighting speed not cheap Cina chipset...
Also Mac Pro trash can have problem on thunderbolt, one only chipset to manage data, work at couple and when you attach a monitor to a thunderbolt the near port slow down transfer rate... absurd... it’s the reason be cause I ever tell that apple stop to produce computer when Jobs dye, and at today we can see only toys not professional computer like 10 years ago.

On a bad reader usb3.0 / hub 3.0 on a mobile workstation hp I reach from 80 to 160mb to transfer from sd to hdd mechanical. From ssd to mechanical i reach 200mb. I should do better if chipset allow you.

Probably a double copy give you faster result
From cf to ssd, from ssd to hdd external


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I cannot really agree with you argumentation cause it works perfectly with larger files like Apple Prores 422HQ. With this type of files, same copy configuration, It stay at the maximum speed level.
Can you explain that if there is some bad bus chipset stuff ? Speed should fall down to ?
Thanks for your reply anyway.

When you work with single large files and with large number of small files you could have different performance. This observation came from old era, where backup could be faster or slower. Real tech causes is about caching system and the way of file management.
At same time my small backup system (usb 3 and esatta nas) that manage 1400 gb backup in 1h of prores shooting ask me 6 hours for dng project of 700 gb.
In past under windows (xp64bit, actually not work) I founded tools that optimize caching during copies that optimize cache of os for small or large files. Today that we need more performance we can found theorically more muscle on hardware but weak point are on software and os management.
If you use os copy tools you have performance X, if you use premiere or Resolve offload tools could performance Y and Z.
The reason that DiT have dedicated tools for copies and backup is not only for parity check during copies but also to optimize performance.


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When you work with single large files and with large number of small files you could have different performance. This observation came from old era, where backup could be faster or slower. Real tech causes is about caching system and the way of file management.
At same time my small backup system (usb 3 and esatta nas) that manage 1400 gb backup in 1h of prores shooting ask me 6 hours for dng project of 700 gb.
In past under windows (xp64bit, actually not work) I founded tools that optimize caching during copies that optimize cache of os for small or large files. Today that we need more performance we can found theorically more muscle on hardware but weak point are on software and os management.
If you use os copy tools you have performance X, if you use premiere or Resolve offload tools could performance Y and Z.
The reason that DiT have dedicated tools for copies and backup is not only for parity check during copies but also to optimize performance.


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Thanks a lot for your reply. I agree with what you said... I know there is a difference between small and large files, specially under 1Mo. I will try with some specialised software to see if there is a difference
BUT :
When I do the same copy which took 3 hours on my external Lacie, on my internal super fast hard drive from Mac, the 250Mo/s rate stay constant. Then the copy only take 25 minutes ! Isn't that strange ?
I think that nothing is logic in all of this and I think there is a weak point I cannot figure it out !

No it’s not a strange issue.
Copy from cfast to ssd is one direction from external to internal, from chipset thunderbolt to pciexpress
Copy from cfast to usb3 hd is dual direction from cfast to computer chipset then from the same small chipset cache again to your out usb 3.
Usb mean Universal Serial Bus, that mean every iteration must attend the end of previous. Also if is fast thunderbolt and usb 3, usb 3 adapter probably is the bottleneck.
Me too when I backup file I used to move from esata ssd reader for Bmpc4k to usb 3 backup hdd, when I can’t use esata reader and I must use usb 3 docking station for in and out I need to attend many more time for the same reason, on a very different kind of hardware.
I don’t know very well the thunderbolt protocols but I think that if you have a thunderbolt cfast reader probably you avoid the bottleneck, but I don’t know if exist and how many cost of it.



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As I understand you try to copy from USB3 CFast reader to external USB3 drive. If you do so you most possibly use the USB3 twice and get a half of USB throughput. You should thoroughly analyze your computer and find USB connectors belonging to different XHCI controllers. My computer has 2 XHCI controllers.

If your computer has only one XHCI controller then at least one drive (CFast or external HDD) could be attached to SATA instead. Either use CFast/SATA adapter or just take the HDD out of enclosure and attach it directly.

Also, be warned that CinemaDNG is a set of small files in one directory. It's quite difficult for the OS to handle such directories. Maybe it could be easier to copy parts of source to different places and then move them to one place.As a variant, if you use an Operating System and not the Graphic Malware Loader (You understand what I mean) you could just use something like

# tar zcvf output_directory/output_archive.tgz input_directory

It writes a single archive file which could then be unarchived as needed, and operating the single file is faster.

Hello guys,
Thanks for your answers. I investigated with some friends and with some different configurations : Hackintosh, MacBook Pro, Mac book air, directly connected to the computer or with a thunderbolt hub... It's always the same : it slow down from 100mo/s (normal 5600 rpm hard drive) to 30mo/s. Mac OS handle easily the big prores but not the multiple small DNG files... We didn't find a solution.
We have to back-up on location so we have to use laptop. The USB-C / thunderbolt 3 of the new 15' MacBook Pro should handle it. Actually it handle it if I replace the mechanical hard drive by SSD... So it looks like it's not about the type of connections (USB / Thunderbolt ...etc) but maybe OS ?
If somebody red something about it somewhere else I would be pleased to get informed.

Cheer everybody

PS: I tried with the DIT software call HEDGE and it didn't change anything. The same with ShotPutPro

Write a command file to copy files to, say, 10 different directories, and then MOVE them to single one.

Write a command file to copy files to, say, 10 different directories, and then MOVE them to single one.

Could be an idea, but I have no idea how to do it. Then is it really safe to backup our precious material on a set ? Then, with this trick, we will not be able to use a DIT software.So we will not be able to check that the copy was 100% good, and no check-sum file.

Then is it really safe to backup our precious material on a set ? Then, with this trick, we will not be able to use a DIT software.So we will not be able to check that the copy was 100% good, and no check-sum file.

Yes is the best idea be cause you have a single only copy of your precious data and as soon as possible you must duplicate.
Davinci, also in the free version have a tool to copy with checksum verification of shooting

Then is it really safe to backup our precious material on a set ? Then, with this trick, we will not be able to use a DIT software.So we will not be able to check that the copy was 100% good, and no check-sum file.

Yes is the best idea be cause you have a single only copy of your precious data and as soon as possible you must duplicate.
Davinci, also in the free version have a tool to copy with checksum verification of shooting

I know all of that, but I think that Anatoly said I should use a script that write on different directories, which mean in different folder of the same hard drive. I think to speed up the copy. It looks like a software trick, but not sure it works and it doesn't change nothing with the duplication of the material.

Exemple : 10 takes (01,02,03...)
10 folders on the same drive : A,B,C...Etc

Take 01 goes in folder A, 02 on B, 03 on C etc...

Maybe I'm wrong... tell me !

On recent os not work, in old os like seven I remember teracopy software that speed up copy using parallel copy, today when I copy more files at same time the final result of speed copy is the same of single copy.


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On recent os not work, in old os like seven I remember teracopy software that speed up copy using parallel copy, today when I copy more files at same time the final result of speed copy is the same of single copy.


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Good to know thank you