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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

closed as primarily opinion-based by LiveWireBT, Zanna, Marcel Stimberg, muru, Eric Carvalho Jan 4 '17 at 16:11

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the 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. – J. M. Becker 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. – J. M. Becker Oct 7 '13 at 23:33
  • I think this question should be closed according to help center. This question was tagged and is about (ARM) chromebooks, yet by default these don't boot unverified external media. A differentiation of class 10 SD cards and USB 3.0 flash drives is difficult, almost impossible on this level, they are all NAND storage devices, as are SSDs/SSMs. USB drives can come in all forms and sizes which relates to the actual architecture and hardware inside, performance can range between terribly slow SD cards and decent SSDs. More info can be found in the Linaro and LWN articles I posted below. – LiveWireBT Jan 4 '17 at 4:45
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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 (600 MB/sec). 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 (60 MB/sec) and 12Mbps (1.5 MB/sec) 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.

  • 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
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    Also SD cards have less life – totti Mar 1 '13 at 16:58
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    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. superuser.com/questions/660155/…. 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
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    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
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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/write 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 an SD card - as Class X (super fast).

  • Can I dare to suggest you attach some useful references that support the information you're presenting? – JorgeArtware Dec 7 '15 at 3:49
  • wiki.linaro.org/WorkingGroups/KernelArchived/Projects/…: Most modern memory cards contain a single NAND flash chip and a smaller controller chip that provides a high-level interface to the data, implemented with a microcontroller that runs software which understands the host protocol (MMC, USB, ATA, ...) and abstracts the block allocation, bad block management, wear leveling and garbage collection that is necessary to be done on the NAND chip. See also lwn.net/Articles/428584 for a detailed description of some of the concepts. – LiveWireBT Jan 4 '17 at 4:18
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A USB 3.0 Flash Drive is almost always preferable to an SD Card when booting an OS. The thing about booting Operating Systems is that 4K Read/Write Speed dictate the experience more than the sequential Read/Write Speed (the usual advertised speed).

Unfortunately, most USB manufacturers don't give a baseline speed for 4K Read/Write and the only thing SD Cards have to have is a minimal sequential write speed (the Speed Classes 4,6,10, etc).

Therefor, you have to test the drives you want to use yourself using bench-marking software (such as CrystalDiskMark, etc).

Generally speaking, any USB 3.0 Flash Drive from a fairly reputable manufacturer will easily outperform any SD Card in both Sequential and 4K Read/Writes. In my experiences I've had MicroSD Cards that struggled to even reach the Speed Classes! One last thing for other people to consider is the available amount of USB ports and their Generation. You might find that your computer may only have 1 or 2 USB ports, so you wouldn't have room for other peripherals.

P.S I have found that Amazon reviews for any particular Flash Drive/SD Card usually contain some Benchmarks to gauge overall performance.

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