Ask Ubuntu is a question and answer site for Ubuntu users and developers. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I recently purchased a Chromebook (ARM). It has an SD card reader and a USB 3.0 port, but I have neither an SD card nor a USB 3.0 flash drive!

If I were to boot from Ubuntu on one of those two devices, which would give me better performance? Which should I purchase?

To be clear, the devices I'm choosing from are:

  • Class 10 SD card
  • USB 3.0 flash drive
share|improve this question
I was reading that booting from the ARM Chromebook USB 3.0 had some sort of problem in the past. I wasn't able to find any good recent info though, so might want to test it out. – TechZilla Oct 7 '13 at 23:28
I also wanted to mention, I prefer using a class 10 UHS-I SD Card. The Chromebook only has those two USB ports, and only one being 3.0, so I felt it was best to keep them free. – TechZilla Oct 7 '13 at 23:33
up vote 10 down vote accepted

I would like to answer about transfer rate.

Transfer rate for:

SD Card

enter image description here

USB 3.0

There are currently three speed modes defined by the latest USB 3.0 specification. They are SuperSpeed, Hi-Speed and Full-Speed.

The new SuperSpeed mode has a transfer rate of 4.8Gbps. While the specification retains Hi-Speed and Full-Speed USB mode, commonly known as USB 2.0 and 1.1 respectively, the slower modes still operate at 480Mbps and 12Mbps respectively and are kept to maintain backward compatibility. Check out this page for a comparison between USB 3.0 and other competing interfaces such as eSATA, FireWire 800 and Thunderbolt.

I suggest you to use flash drive to boot.

share|improve this answer
Thank you for your answer—I thought perhaps something other than transfer rate could come into play here, but I know nothing about this stuff! Your post mentions "this page", but there doesn't appear to be a link. Would you mind pasting the URL? – user136615 Mar 1 '13 at 7:03
Here's a good comparison of Class 10 SD cards. And Here's one for USB 3.0 device sas you can see USB 3.0 is faster. – Uri Herrera Mar 1 '13 at 8:32
Also SD cards have less life – totti Mar 1 '13 at 16:58
A pen drive can have USB 3.0 but a slow flash memory inside, and perform worse than a drive with USB 2.0 with a fast flash memory inside.…. Thus you need to check (and I don't know how) if the USB pen is fast, not just by judging the USB protocol version. – Mads Skjern Nov 4 '14 at 9:18
I think it's slightly disengenuous to compare the minimum SD card speeds with the maximum allowable USB speeds. I can't find anywhere a USB 3.0 that actually operates at 4.8Gbps, and almost any SD card gets at least 70Mbps, which is about average for USB thumb drives. – KyleMit Nov 28 '14 at 6:58

I think there is perhaps, I say perhaps, an over riding consideration on the selection. The class level for the SD Card is there because it is basically saying these are the read/wrote speeds of the memory on the SD card. It is not an IO speed limitation. The USB stick issue/specification that is being sited is indeed the actual data transfer rate capability. HOWEVER, it does NOT say anything about the capability of the actual media on the two sides of the USB interface.
So my thought on this is, we have to dig a little deeper!
On the USB stick is Flash Memory - basically the SAME memory types, with the same limitation as the memory on the SD Card.
So - this means that if the Memory on the USB 3 Memory Stick in Class 10 then that will be the limitation. If the memory on the USB 3 stick is Class 2 then that will be the limitation.
Basically - we can NOT assume that because the interface is USB 3 that the transfer rate will be the same as the USB 3 specification - in this case.
I would also submit that if Memory, for use on a USB stick was actually much faster - then it would very likely be available on am SD card - as Class X (super fast)

share|improve this answer
Can I dare to suggest you attach some useful references that support the information you're presenting? – JorgeArtware Dec 7 '15 at 3:49

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.