A little over a year ago, I wrote an article that documented how I was using an external drive with Dropbox. Over the last year, I’ve been trying several methods in the hopes of finding the perfect solution.
This article is where I will be documenting my use of a Micro SD card to store Dropbox content. I’m using an adapter that takes a Micro SD card and allows you to stick it into your MacBook’s SD card slot and sit flush with the edge. I’m using this BASEQI adapter and this PNY 128GB card and it looks like this:
I started researching Micro SD cards and their speed, but quickly had to just say, “Well, this is probably as fast as it is going to get”. My Micro SD card is what is called a “U1” card. Here is a table that shows the different speeds of SD cards, taken from sdcard.org along with all the logos you will see on the SD card and it’s packaging:
As it turns out, it wasn’t as fast as it was going to get, since I got a U1 Micro SD card which is 1/3 as fast as the U3 Micro SD card.
It is worth noting, when looking at these speed levels, the difference between the lowercase “b” and the uppercase “B”. When you see 100 Mbps, that means Megabits per second. But there are 8 bits in a byte. When you see 100 MBps or 100 MB/s, that means MegaBytes per second, or 8 times faster.
Now that we know that my new U1 Micro SD card is going to operate at 10 MegaBytes per second, let’s compare this to the SanDisk USB drive I was using before… That used “USB 3” (yes, there is a difference between USB and USB 3 – USB 3 is loads faster). Since my U1 Micro SD card is 10 MB/sec, and USB 3 was a minimum of 100 MB/sec, I already know that this is going to be at least ten times slower.
However, USB 3 can burst up to 640 MB/sec, so while my 10 MB/sec Micro SD card is guaranteed to be at least 10 times slower – it could be 64 times slower…
USB 3 can range anywhere between 100 MB/sec to the theoretical maximum of 640 MB/sec. So right off the bat I know that my Micro SD card won’t operate as fast as the previous USB 3 SanDisk drive. If you can find a Micro SD card that is U3, you’ll be at least three times faster than a U1 Micro SD card.
- USB 3 – 640 MegaBytes per second
- U3 Micro SD – 30 MegaBytes per second
- U1 Micro SD – 10 MegaBytes per second
But I’m using this for Dropbox, so does any of this even matter?
On day one, it felt like it was going to matter, and that this Micro SD card just wasn’t going to work. Moving large volumes of files from the USB 3 drive to the Micro SD card took a really long time. And when I say a really long time, I mean that it took the better part of a day (closer to 18 hours than 1 hour).
I also felt like it was slowing the whole MacBook down. Over the next few days I decided to change Dropbox’s Selective Sync for a couple of folders. I wanted to have as much of my Dropbox on my SD card as I could, so I began downloading large, multi-gigabyte folders to the Micro SD card that I didn’t have on the old USB drive.
This took longer than I expected. Moving Dropbox from my USB drive to the Micro SD card was one thing, but downloading just one 2GB folder from Dropbox took the better part of a day on very high-speed internet.
I started out using exFAT as the file format on the Micro SD card, but quickly reformatted that to OSX Extended since I had read that it made a big difference in speeding up access to an external drive.
I asked over on StackOverflow to see if the format of the SD card played a big role in the speed of the card. I was thinking that the internet speeds weren’t the problem, so possibly it was an IO issue on the card, but the consensus was that the formatting of the drive doesn’t have as much to do with the drive speed (ie: USB3 is faster than Micro SD U3 is faster than Micro SD U1).
I’d like to experiment with exFAT, OSX Extended, and OSX Extended Journaled, running speed tests on the drives with each format, but I’m worried about how much time it will take.
As of today, I’ve synced everything that I have room to sync from Dropbox. I have about 5GB free on my 128GB Micro SD card. But now that I’m done with the most of my syncing, the MacBook is performing normal again. I intend to leave things for a while and see how they are doing, but as of now, it seems like this is an acceptable solution once you have a chance to get everything synced up.
UPDATE: June 5, 2016
I’ve been experimenting with something that I was confident was going to be a failure: running applications from the Micro SD card. I had done this on the USB 3 drive, so I thought I would give this a chance on Micro SD as well.
The first application I moved over was pretty lightweight and low-usage: flux. Flux helps to adjust the color of your screen so that you get warmer tones as you get later into the night. That worked out very well, and I never even noticed a change in the way things loaded.
With the success of Flux under my belt, I decided to do something drastic: I moved Google Chrome over to the Micro SD card. Google Chrome is my primary web browser, so I was sure this would be a total bust, but… here it is, a day later and, believe it or not, I’m updating this blog post in Google Chrome on the Micro SD card. I don’t really understand why, it works exactly as fast as when it was on the SSD hard drive.
I’m going to try moving more CPU-intensive apps over to the Micro SD card. It would be interesting if something like Photoshop or Garageband could run off of the Micro SD. I kind of doubt that would work, but I’ve obviously been wrong before. We’ll see.
UPDATE: June 8, 2016
For the past few days, running Dropbox on this Micro SD card has been working out perfectly. So I decided to add applications to the Micro SD card to see how well they could run on it as well. I found a problem that you should be aware of…
I took an overnight trip and took a lot of photos on my smartphone; I knew these were going to need to get synced up with Dropbox, so when I came home, I opened up my MacBook and watched to see what would happen.
Well, it turns out that Dropbox went to work right away to sync the new photos to the Micro SD card. HOWEVER, I had just moved Google Chrome to the Micro SD card. As it turns out, while Dropbox was downloading the new photos, Google Chrome wouldn’t even load.
Now then, I need to go back and clarify exactly what is happening here, because this setup does in fact work pretty well if you aren’t doing what I am doing.
So I was trying to use Dropbox with a U1 Micro SD card as the storage location, AND have applications that I would run directly from the same U1 Micro SD card to save space on my MacBook’s internal SSD.
As long as Dropbox isn’t syncing data and downloading files, this works flawlessly. I have been able to even run Google Chrome from the Micro SD card without any noticeable change in speed. But while Dropbox is downloading data, any application on the Micro SD card will not operate at an acceptable speed.