4 ms·
Why would that be? Can you provide more details? I thought SSDs are always faster than HDD
by murukesh_s 8y ago
Why would that be? Can you provide more details? I thought SSDs are always faster than HDD
- ddorian43 8y agoHDD are fast ~enough on sequential read/write in this scenario.
- akvadrako 8y agoNot at all - SSDs are much faster. One of the fastest HDDs on storagereview.com is the WD Black 6TB, with a sustained 218MB/s. While one of the faster SSDs is an Intel 750 at 2400MB/s.
- ddorian43 8y agoIf you have some HDD, and you RAID them, processing video should be mostly sequential read/write, so it should work on HDD. I know SSD is faster, but it depends on what the workload requires.
- Dylan16807 8y agoSo let's say you're working on ten hours of 8k footage. If you go with 1.2TB 750s... oh you can't actually fit 20-100 of those in a single workstation.[1] So maybe we back off to a NAS attached over a 40Gbps cable. 40 of those hard drives will be a lot cheaper than 20 of those SSDs. If we grossly overestimate seek times, despite how big the frames are, we might estimate 125MB/s per drive. That's enough to completely saturate the connection. Oh, and the array has 10 times the capacity. [1] 20 assumes a lower framerate and generous compression. 100 assumes 60fps 12-bit at a lossless 3:1 compression. If "raw" is taken completely literally then 10 hours of footage could require 300 of them (and some of the math would have to be redone).
- akvadrako 8y agoI don't question that HDDs are much cheaper - but even with your franken 40-drive stripping solution, you are only getting as much performance as 3 SSDs (40Gbps < 3 * 2.4GB/s). Of course for video production you would choose slower, larger SSDs but still get an order of magnitude more performance, very handy when seeking through footage.
- Dylan16807 8y agoHow much performance do you actually need, though? As long as you can load 60 * k arbitrary frames per second then you can skip around at will. Being capped at the equivalent of 3 or 10 high-end SSDs isn't problem if there's no good way to fit more than that with any tech. And you don't exactly need to stripe them all. You could set it up as a blob storage, maybe storing each blob twice so you can distribute reads better.
- dogma1138 8y agoVideo editing is not sequential by any means, I can maybe give that to encoding / transcoding an existing file on disk (if both the disk and the file system can ensure that a file in the 100's of GB or even a few TB's in size can be sequential) but with editing you jump back and forth between a multitude of different frames across the entire timeline of the video in the file each of those frames is a few MB's in size at these resolutions and at these file sizes it's effectively the same as randomly accessing small files on an HDD which is never exactly fast.
- Dylan16807 8y agoIn the absolute worst case of frames that are on opposite ends of the disk and compressed to 20MB each, you're still spending less than 20% of your time seeking. When you take random-access and make the data chunks big enough, it becomes sequential-access. Raw 8k footage is above this threshold.
- dogma1138 8y agoTry editing a 4K raw video on an HDD and come back to me it’s nearly utterly impossible to do so without high double digit dropped frame count.
- Dylan16807 8y agoIn general, for raw 4k, a single HDD doesn't have enough bandwidth, and a single SSD isn't big enough. But the main advantage of the SSD, IOPS, becomes less and less important as bitrates increase. As you go bigger and bigger, using storage arrays no matter what drive tech, hard drives start to be able to perform perfectly fine at lower price levels, while also fitting much more data.