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06-04-2016, 12:14 PM   #1
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Does alternating SD cards result in greater data throughput?

First, I have tried to read the other card-speed threads, but not quite found what I'm trying to understand (I don't have the K1 yet but plan to get one, so I can't test it myself), so forgive me if this is already covered somewhere, and please point me there if so. (Almost hijacked one of the other threads but I guess this a new question)

I have read that it seems that writing the same data to both cards seems to double the write time required (given that the cards have similar write speed). To me this seems to indicate that only one card is written at the time, which seems like a waste since the data is sitting there ready to be written (sure it may be a bus limitation but then that would be a strange design choice, forfeiting double write speed to save a couple of $, and then i really mean a few and not 20$), but this got me worried that what I thought would be an advantage of having multiple cards, may not be the case after all, my question is:

Say if you configure it to save only raw, and alternating cards for each image (say odd image numbers go to card 1 and even numbers to card 2), I would have thought that while image 1 is being written to card 1, image 2 can start being written to card 2 even if image 1 isn't done yet, thus increasing the total data throughput, so my question is, does the K1 work like that, or does it still just write one image at the time no matter the number of cards and settings?

I guess a test for that could be to shoot a burst of X images, and compare total write times when set to write on one card, compared to when configured to write every second image on each card.

(Thanks for any responses, and please refrain from "pentax is doomed"-blaming, I think Pentax is doing great and that the K1 seems to be a great camera, and understand that choices have to be made and money saved in order to reach the current price, but I want to find out about this, and yes, if it is so I'd think it's an unnecessary limitation and would not agree with this particular few-$-saved vs feature-decision, but I'm by no means saying the K1 a bad buy in any way, only that I would have preferred to pay a few $ extra for that)

06-04-2016, 01:43 PM   #2
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Not 100% sure what the question is but the k-1 writes to only one card at a time. Saving to both cards takes twice as long.
06-04-2016, 01:53 PM   #3
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QuoteOriginally posted by Igor123 Quote
... I guess a test for that could be to shoot a burst of X images, and compare total write times when set to write on one card, compared to when configured to write every second image on each card.

...
I don't think things can be configured that way so there is no test that can be performed.

The camera does not operate like a RAID array and write/mirror to both cards/drives at once. I don't know what this change would cost but computers don't do this, either, unless they have a RAID controller (seems like it is not an uncommon feature).

I agree that writing the same image to both cards for redundancy is not as convenient as I thought it would be. I don't recall coming across complaints of double write time for the K3 cameras.. but I didn't really read much about those cameras, either !

I take pictures of things slowly enough that the longer write times wouldn't matter. I presume there would be little impact to practical use of the camera because the buffer would hold enough images for my here and there approach..

How this increased write time impacts image review time would be interesting to learn. If there is no impact there.. then the feature is still very usable for single image (rather than burst) use.
06-04-2016, 01:57 PM   #4
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QuoteOriginally posted by Igor123 Quote
Say if you configure it to save only raw, and alternating cards for each image (say odd image numbers go to card 1 and even numbers to card 2), I would have thought that while image 1 is being written to card 1, image 2 can start being written to card 2 even if image 1 isn't done yet, thus increasing the total data throughput, so my question is, does the K1 work like that, or does it still just write one image at the time no matter the number of cards and settings?
There is no such setting. You can either have the camera save to one card, save to both at once, or split RAW and JPEG.

Write time tests can be found here:
Pentax K-1 Review - Performance and Burst Mode | PentaxForums.com Reviews

And @jatrax is right, the camera can only write to one slot at a time. Compounded by the relatively slow write speed, this can result in quite a long wait at times (though the camera doesn't "lock up" while writing unless you have geometric distortion correction enabled in JPEG).


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06-04-2016, 02:04 PM   #5
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Ok, sorry to hear that but then I got my answer, thanks!

Edit: I don't know if it's common practise, and I can't find a control for it, but for my part the thread can be closed now, but if that's not how it's done, by all means, let it be =)
07-22-2016, 12:02 PM   #6
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I bought a 128gb ultra and a 64gb ultra, put them in so that the jpg writes to the 64 and the dng writes to the 128. Seems to work fine for me.
07-22-2016, 12:13 PM   #7
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Unless there are separate controllers for the two SD slots, there is no advantage in alternating read/write process to improve performance. Until the camera makers start putting UHSII high performance bus into the DSLR (some day it will be the standard), the bottleneck is still in the bus and speed of the cards.
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