Store video files on USB, SD card, microSD, or external hard drive?

Question

Working with raw .mts (MP4) video scenes that are about 6.5 GB in size each (but automatically partitioned by the camcorder into separate 10-minute chunks), what arguments are there for not storing them on SD cards?

• From experience, USB drives are high-risk storage devices since they can become corrupted without warning, rendering all data on them inaccessible.
• External hard drives are just too heavy.

This leaves SD cards, they are lightweight. Is it a bad idea to store raw video files on SD cards? How about microSD cards?

Is there a better storage device than all four?

Answer 1

Generally, it’s a bad idea to store data on SD or micro SD cards for any substantial period of time. If you’re a hobbyist, traveling, and plan to transfer to a hard drive when you get home, that’s fine. But if you’re a traveling media specialist, you want to get your data off of SD/micro SD as soon as possible, for a number of reasons;

1. Those cards are easily corrupted, because they have very little shielding against electromagnetic or static discharge, and don’t have built in error correction circuitry. They are absolutely higher risk than USB hard drives.
2. They are easy to lose, because they’re small.
3. They break. The plastic wears down over time, especially after several hundred insert cycles. The thin strips of plastic that separate the contact “teeth” of SD cards are especially fragile, and when they break off, they can damage your camera.
4. They’re made and priced to cycle data. It’s more economical to store long-term data on media designed for that purpose. If you bought a new SD card every time it was full of photos, you’d be throwing money away.
5. They’re not designed for random access. They’re designed to write data quickly and sequentially, but reading it quickly isn’t a priority, and constant random read/writes would not only be very slow, but would also shorten the card’s lifespan.

What you should use instead depends on how you intend to use it; how long you intend to keep the data, how often you plan to read the data, how quickly you need to read the data, and how much money you’re willing to spend.

No, portable hard drives aren’t as reliable as desktop ones, but they are more... portable. Portable SSDs are faster and more reliable than spinning metal, but they’re more expensive and have lower capacity. If you really want to protect your data while traveling, you can get portable 2-drive RAIDs, with either SSDs or HDDs, but they’ll be at least double the price of their single-disk counterparts. If you’re a DIT working on a major motion picture, you might possibly lose your job for not using an actual RAID. If you’re a digital finisher, you probably have all of the above, plus maybe LTO. Yes, tapes are still the most economical way to store data long-term, and they have a lifespan of around 30 years.

Answer 2

I strongly advice against microSD cards because they will get lost. They're just too tiny.

There are external SSDs which weigh not much, 50g maybe 100g, I think this is not much weight. Of course you need a way to attach the drive to the camcorder or rig, adding a bit more weight. When filming hand-held, the additional weight and a different center of weight might be an issue which plays a larger role.

Since you mention data loss with USB: this can actually happen at any time with any technology. I've heard people having such a problem with SD cards too and experienced it myself. SD cards don't naturally perform better than USB drives here, because the interface and storage technology is not the problem. The camera's operating system is causing these write errors, especially when using an improper file system. Therefore, using SD cards does not automatically protect you from errors.

Whether you lose access to all data or just the last written file depends largely on the file system, for mass-market cameras they usually use inferior file systems, like the out-dated FAT32. Hence, the fear to lose all data due to one write error is not unrealistic.

Keep an eye on write speed and general compatibility. The camcorder's manual should contain all relevant information. SD cards need to be fast enough to store raw data. SSDs can be faster, but not faster then the USB connection, and camcorder capabilities allow.

High-end cameras use PCI Express as an interface to the SSD for this reason or have proprietary systems. CFast cards are used too. I consider all these high-end systems to be better than the ones you mentioned, but it will be useless to think about it this way if you don't have a camera which could make use of these. You first should ask yourself what exactly you will film, what requirements result, and finally what gear fulfills the requirements.

It's not helpful to find out what's the best storage solution in existance, if it's over the budget and a simpler solution would work for your case too. If you want to film scenes that are unique or cannot be easily repeated and the budget is low, just try to buy/rent a 2nd camera and run both at the same time for the critical scenes. This way you're not only protected against storage failures but also against any camera failures, because it's highly unlikely that both cameras fail at the same time. Have a laptop on the set to create file backups as needed.