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     David Council updated 1 week, 2 days ago 6 Members · 15 Posts
  • David Council

    March 25, 2021 at 11:32 pm

    Hello all.

    I’m in the process of speccing a new edit machine and am wondering if there is an equation I can use to calculate how fast I need my disks to run to able to manage different flavours of footage.

    For instance, I frequently use Raw 4k footage from a Sony F55, which Sony tells us is 1000Mbps / 125 MBps.

    To edit one steam of this footage in real time (let’s assume my GPU / CPU / RAM are equal to the task) how much faster than 125MBps do I need my drives to run? If I’m editing two streams of the footage, do I simply need to double the numbers, or is life more complicated than that?

    I will probably never need to edit more than four streams of this footage at one time, but I’m suspecting drives capable of 600MBps sustained read / write won’t be up to the task.

    I’m happy to invest in something like the OWC Accelsior 4M2 for it’s eye-bleeding 6000MBps if I really need to, but I’d like to be able to calculate exactly what is necessary if I can.

    Thanks all, in anticipation of useful equations.


  • Joseph Owens

    March 25, 2021 at 11:45 pm

    BlackMagic supplies an application called “Disk Speed Test” which isn’t theoretical at all.

    What it tells you is your current configuration’s performance and you can extrapolate from that.

    It is slightly more complicated than doubling up the numbers since the CPU/GPU balance will come into play once the Resolve application is ingesting and decoding/decompressing your source media. The demands between high-bitrate non- or lightly-compressed material is different from lower bitrate, highly compressed media.


  • David Council

    March 26, 2021 at 7:09 am

    Hello Joseph.

    I did not ask how to measure a disk’s speed, but thanks anyway.

    Also, thanks for pointing out that different media will have different system demands (who knew?) even though I specifically removed CPU/GPU from the equation.

    I don’t mind that you don’t know the answer, but it seems to be a bit of a waste of your time writing an irrelevant post to illustrate that you didn’t even understand the question.


  • Jeremy Garchow

    March 26, 2021 at 1:35 pm

    More speed is better. At some point you will hit a decompression/processing limit as well. The NVMe storage is absolutely stunning. It is also very expensive. At the least, you’re going to want a 5 drive raid 5 setup. That will give you the capacity of 4 drives, and the fifth is used for redundancy information in the case of a hard drive failure. I have a, small (palm of your hand) 4TB Thunderbolt 3 ssd and it does 1000MB/sec and handily edits 5k red raw from FCPX and a 16” laptop without a hitch. But it’s a single drive and has no redundancy so I have backup measures in play.

  • David Council

    March 26, 2021 at 3:07 pm

    Thanks Jeremy.

    I get that faster is better, I’d just like to be able to make more precise calculations, as this is going to be a sizeable investment and I want to put the money in the right place.

    Yes, the NVMe drives are stellar, but do 4 streams of footage that run at a total of 600MBps need storage that runs at 6000MBps? Would it run on a sata ssd raid at 3000MBps for instance? Maybe even an external Thunderbolt 3 raid at 2300MBps? Not being able to work this out is what is exercising me!

    If I’m going to plump for NVMe storage, I think it’ll be striped in raid 0 with a daily backup to slower / cheaper storage …

    Thanks again.


  • Jeremy Garchow

    March 26, 2021 at 3:15 pm

    Drive speed will make a difference, but depending on what you are doing and how much processing, drive speed won’t be the bottle neck. If you have a sustained 1000MB/sec, you should be able to do two streams of raw playback without any trouble. You don’t need 6000MB/sec, but if you need to work and transfer files at the same time, 6000MB/sec comes in very handy.

  • Jim Curtis

    March 26, 2021 at 6:23 pm

    You can’t remove the CPU/GPU from the equation for compressed codecs, because there’s an inevitable amount of processing needed to decompress compressed video on the fly. RAW formats are especially hard on processors.

    If you’re still shopping, my advice is to buy a lot more computer than you think you’ll need, because every year, it seems, it’s 8K, 12K, 16K, and so on.

    My deal is to spend money until it hurts, because I’ll be glad I did later.

  • David Council

    March 26, 2021 at 9:29 pm

    Hello Jim.

    Thanks for your reply.

    I’m asking a question about hard drives. To make sure the replies are about hard drives, I suggested we assume the CPU / GPU are good enough to handle what’s thrown at them. I don’t think anyone needs reminded that different codecs cause different stresses on cpu / gpu.

    I’m not sure how your business is doing, but if it’s ok with you, I’m not going to “spend money until it hurts” if it’s completely unnecessary. To put it a little more elegantly “Who breaks a butterfly on a wheel?”


  • David Council

    March 26, 2021 at 9:32 pm

    Hey Jeremy.

    Thanks for your response. The assumptions I’m making are broadly in line with what you’re suggesting. I’m just hoping to find someone in a white coat who can share practical numbers so I can estimate at what point the hard drives would cause a bottleneck.



  • David Baud

    March 27, 2021 at 6:56 pm

    Hmmm… I am with Joseph and Jim on this one. If you are concerned to get the right hard drives for your work using DaVinci Resolve, it does not make sense to me to look at your hard drives configuration only, separate from your GPU/CPU selection. As you may already know, reading and writing a movie file, is not only about the speed of your hard drive but also how fast the file is decoded and encoded.

    “For instance, I frequently use Raw 4k footage from a Sony F55, which Sony tells us is 1000Mbps / 125 MBps.”

    This number does not mean much regarding the need for your hard drive speed. It tells you the bandwidth needed when recording RAW footage (storage space). Sony RAW is not as compressed as XAVC-I or DNxHD file formats. Usually uncompressed format is faster to encode and decode, but again it depends on other parameters in your computer system like your CPU & GPU. Faster is your drive, better is your chance to avoid the bottleneck of reading/writing your file and sending the data to the next processing phase in CPU/GPU. Another concern is the space left on your drive: a full hard drive can be much slower than an empty one.

    Unless you have only one type of file format you are working with (which in real post-production workflow does not happen), I believe it will be very difficult to get any meaningful speed number that will help you to decide which drive system to get. My recommendation would be to get the fastest drive system you can for your budget, based on the intended task.

    I am a colorist and finishing editor, working on documentary and feature film projects. I work with all kind of footage from Arri, RED, Canon, Sony, GoPro… in RAW, Log or compressed formats. From SD to 8K frame sizes. In order to handle the variety of formats, our main computer system is configured with a mix of storage systems, tailored to the usage we need. The fastest we have is based on M.2 NVMe memory, 4 X 2TB attached directly to a PCIe card, RAID-0 mounted with speed rate up to 12,000 MB/s. This is ideal for color grading using process intensive nodes such as noise reduction/grain or other OFX plugins.

    We also use SSD and traditional “spin disks”external hard drive, in RAID configuration or not. These systems give us anywhere from 200 MB/s to 4,000 MB/s rates speed. Some of them are used for media caches, backup redundancy, or less intensive files processing.

    I hope this information will help you in your decision making.

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