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USB3 Flash stick, take-2

March 29, 2016 — BarryK
I recently purchased a SanDisk Ultra Fit USB3 32GB Flash stick, as reported here:
http://bkhome.org/news/201603/quirky-xerus-works-well.html

As I posted, I have concerns about overheating, and flakey insertion, so have put it aside for occasional use.

So, I needed to buy another USB3 Flash stick, and I purchased the Samsung Bar Metallic 32GB stick:
http://www.harveynorman.com.au/computers-tablets/networking-hard-drives/usb-hard-drives/samsung-bar-metallic-usb-3-0-32gb-flash-drive.html

It only cost AU$16, Easter-sale at Harvey Norman.

It is working well, only gets slightly warm -- well, it is a big hunk of metal, so dissipates the heat very well.
No issues with plugging it in.

The only downside is no activity light. I do so miss that!

One interesting thing. Both of these drives state "130MB/s".
However, running this:

# hdparm -t --direct /dev/sdb

Returns a read speed of about 30MB/s, for both of them. Plug it into a USB2 socket, still get 30MB/s!

The reason for this discrepancy is the cache in the Flash drive.
The above test is bypassing the cache. Yeah, maybe reading from the cache will give 130MB/s, but that is so misleading.
If you were streaming video off the stick, it would be coming off at 30MB/s, not 130MB/s.

The reason I got the same speed in a USB2 socket, is because the limiting factor is the drive itself, not the USB2 max transfer rate (USB 2.0 is capable of up to 60MB/s).

For comparison, I ran the 'hdparm' test on one of my USB2 sticks, and got about 12MB/s.

This is making me wonder whether you would really notice much difference in performance, whether the USB3 Flash stick is plugged into a USB3 or USB2 socket!

Tags: linux