SDHC cards - real speeds

I was planning to order another couple of SDHC cards.
Class 10 seems to be the fast option.
However I am seeing different speeds claimed for different cards.

claims up to 17BM/sec write speed.

claims 30MB/sec and UHS-1 compatibility.
So given that the Transcend is £8.45 and the San Disk is £10.04 you seem
to get a lot of extra speed for not much more money.
Then again, the discussion (which I'm still reading)

seems to suggest that there may be limitations in the hardware/firmware
and the Pi may also not be able to fully drive a UHS-1 card which requires
a higher voltage.
So is it a waste of money getting the fastest possible card?
Dave R
Reply to
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I went for the Sandisk 30MB/sec, 8G card, and the speed difference is noticable over all other cards I have tried.
-- mrr
Reply to
Morten Reistad
What do you want it for?
AIUI Class 10 cards are fast for saving of large files, but utterly dire for random writes (small files or using as swap): Then again, the discussion (which I'm still reading)
UHS-1 requires a /lower/ (signalling) voltage (while keeping the supply voltage at 3.3V). AIUI the RPi does support that - indeed I think the Pi SD card interface is quicker than the BeagleBoard (TI OMAP). Note that thread is from 2012 while the drivers were still evolving - in particular the MMC was clocked at half speed for a while.
I suspect so, but for other reasons.
Reply to
Theo Markettos
On 01 Jul 2013 22:51:25 +0100 (BST), Theo Markettos declaimed the following:
Class 10 cards are rated for streaming a single file on freshly formatted media -- optimal for HD video. Classes 6/4/2 were rated on fragmented I/O (interleaved files, small files, etc.)
So yes -- it is possible that a Class 10 card may be a snail when used for something like an OS image...
	Wulfraed                 Dennis Lee Bieber         AF6VN    HTTP://
Reply to
Dennis Lee Bieber

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