bugsy_malone 666 wrote:So I am understanding that you can use a small SD card containing just the 'boot' bit thats normally on the windows formatted part of the card to boot the Pi to a USB stick.
I wondered whether people have noticed in improvements of performance or if there are any issues with this?
Any changes in performance would depend on the SD card and/or USB flash drive you are using.
SD cards, and often USB flash drives as well, are optimized for sequential read/write performance, while computers typically do a lot of non-sequential (random) I/O. Unfortunately most SD and USB flash devices suck horribly at random I/O, so they are just about the poorest choice for a computer OS drive you could make (SSD drives designed for computer use have much more powerful processors and are much faster at random I/O).
As an example, I have a Patriot 128GB Supersonic Rage 2 Series USB 3.0 Flash Drive, described as follows...
"With read and write speeds of up to 400MB/s (Read) and 300MB/s (Write), the Patriot Supersonic Rage 2 uses high quality MLC NAND coupled with a state of the art IC controller for excellent performance when working with large file transfers."
Did you notice the "Marketing Speak" disclaimer in there? You probably did, because I bolded the text.
This drive is extremely fast when doing sequential I/O, which would be the case when working with large file transfers. Approaching cheap SSD performance.
However, when I tested it for random I/O in Crystal Diskmark I got this:
- Random Read 4KiB (Q= 32,T= 1) : 6.216 MB/s [ 1517.6 IOPS]
- Random Write 4KiB (Q= 32,T= 1) : 0.026 MB/s [ 6.3 IOPS]
- Random Read 4KiB (Q= 1,T= 1) : 5.512 MB/s [ 1345.7 IOPS]
- Random Write 4KiB (Q= 1,T= 1) : 0.010 MB/s [ 2.4 IOPS]
Random reads are only single digit MB/s, and random writes are absolutely abysmal (KB/s)! I've actually gotten better random write numbers from cheap USB 2.0 flash drives.
So anyway, to make a short story long (see what I did there) you'll want a USB drive with good random I/O performance if you are going to use it an an OS drive.
Another option, if you don't need a ton of storage, would be to get a small SSD and a SATA to USB adapter. Small SSD drives are cheap now. Actually cheaper than some high end Micro-SD cards. I imagine even a cheap SSD would outperform most (if not all) Micro-SD cards. Of course I'm in the USA, so the pricing situation might be very different over there in the UK. Here you can find 60GB SSD drives for <$30 ($26.99 is the lowest I found after a quick search), and 120GB SSD drives for < $40 ($37.99).
I hope you found something useful in this rambling post.
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?