There are a few hardware components that immediately come to mind when one thinks about what determines image quality of any particular camera. One thinks about the sensor, the lenses, maybe even the analog to digital converters, but you rarely think about the storage device, even though it’s of the most important factors.
The storage device is often the bottle neck for your data throughput. The stability of the storage device not only reflects on the reliability of the camera, but sometimes can effects image quality. When bits are written incorrectly it can look like noise, artifacts, even dropped frames. When talking about SSD drives specifically, there is a whole separate class of drives which are designed and tested to be much more robust than typical drives and avoid these and other issues. They are called “enterprise” class drives.
Enterprise class drives are built from better materials, are much faster than normal drives, and are much more reliable. They are more reliable because they have enterprise data path protection which is a combination of hardware and software that determines the logic path your data actually takes while being written to the drive, and how it’s read later.
This is an example showing the difference in complexity between a typical drive and an enterprise class drive:
You can see that the complexity of enterprise drives is much higher. The firmware is also tuned for high end use. This means that your precious bits are checked and double checked as they are being written and read to assure that there are no errors, and if there are, the errors are corrected.
If we are taking care to create the best looking images we can we must also take care to store them correctly once the images are created.
When we were picking a drive for the D16 we had many factors to think about. Reliability and speed were most important, but price had to be part of it too. These enterprise drives are not cheap. When Arri charges over $3000 for a 512GB mag it’s because the drive inside costs almost $2000 in the first place. Until recently, you had a lot of choices in SSD brands and models, but not a lot of choices in SSD Class. You had the consumer level drives around $120 – $400, and you had your enterprise level drives that were between $480 – $2000. At that time putting an enterprise class drive inside a camera like ours would have been out of the question. Either the drive would be too small to be useful or the drive would cost the equivalence of half the camera price.
These days there are mid level drives, which are perfect for our camera. The drives are priced between the other two classes, they have the kind of performance and protection we want for our camera, including enterprise data path protection, and are being made by reputable companies.
There is even a slim version of the drive that is only 7mm tall instead of the standard 9.5mm.
The actual drive capacity of the hardware is 512GB, but it has been reduced to 400GB to create buffer space for dynamic wear leveling, meaning that the drive lasts much longer by allowing space for bad sectors over long periods of time. The P400e also has power-loss protection, meaning that if the camera power cuts out suddenly the drives’ onboard capacitors store enough power for the drive to commit all pending write commands before turning off.
But what about lifespan? There are not spec tables setup for our use case, which is very different from normal SSD use. First of all, most SSD use is rated for random read and write, and our use is almost completely sequential read and write. Also the published specs are for 1 year of data retention, which assumes you won’t erase any particular piece of data for 1 year. There is a direct inverse relationship between data retention and life span. So, for instance, if you lower the data retention to one day instead of one year the estimated life cycles go up dramatically. It took a little bit of work, but we estimated the drive life with our Micron dealer and it came out like this: the drive is rated for 1.2 million device hours and with our use case we think it will last at least 5,000 full write cycles before showing any kind of data loss, which means if you wrote the full capacity of the drive 3 times a day (4 hours of raw recording), every single day, it would last over 4 and half years! Most of us won’t shoot 240 minutes of footage in a day, and we won’t shoot every day either, so we estimate the drive will last somewhere between 5 and 10 years even with regular use.
We think reliability and data accuracy are very important parts of any camera, and we believe the Micron P400e will help us make a camera with these attributes.
Thanks for reading, Joe and the Digital Bolex Team