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03-29-2016, 08:50 AM   #1
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Allocation Unit Size

On a whim I tried formatting an SD card in my PC using the normal exFAT system but with a larger than normal Allocation Unit size (4096 K bytes). After creating the DCIM folder I tried it in my K-5 and it worked fine. What's noteworthy is the huge improvement in Lightroom's preview performance on my somewhat underconfigured PC - has this been looked at in detail already or have I found something new? I'm shooting in RAW (DNG) btw.

Cheers

03-29-2016, 09:51 AM   #2
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QuoteOriginally posted by IanG Quote
On a whim I tried formatting an SD card in my PC using the normal exFAT system but with a larger than normal Allocation Unit size (4096 K bytes). After creating the DCIM folder I tried it in my K-5 and it worked fine. What's noteworthy is the huge improvement in Lightroom's preview performance on my somewhat underconfigured PC - has this been looked at in detail already or have I found something new? I'm shooting in RAW (DNG) btw.

Cheers
Because you are shooting RAW (larger files) it may be helping your PC out by giving it less AU to read per file. The only drawback is wasted space. Essentially an AU sacrifices some of its allocation (about 50%). The larger the allocation, the larger the wasted space multiplied by the number of files per card. For a one day shoot on a large enough card, it's probably not a big deal. But if you were on a safari and using larger AU formatted cards, for a 16gb card you might lose the capacity for 10-20 images per card. Not a huge deal, maybe... But if you have no way to d/l the card contents to reuse, you would need additional cards compared to a shooter using smaller AU formatted cards of the same capacity.

On some of my shoots, I've shoot 5-6000 images in one day. It probably would equate to needing 1-2 extra 32gb cards, unless you got crazy and went with AU sizes in the KB range.
03-29-2016, 09:58 AM   #3
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QuoteOriginally posted by IanG Quote
On a whim I tried formatting an SD card in my PC using the normal exFAT system but with a larger than normal Allocation Unit size (4096 K bytes). After creating the DCIM folder I tried it in my K-5 and it worked fine. What's noteworthy is the huge improvement in Lightroom's preview performance on my somewhat underconfigured PC - has this been looked at in detail already or have I found something new? I'm shooting in RAW (DNG) btw.

Cheers
Very interesting information if accurate, you could sell it to Pentax^^ I can tell nothing right now but the allocation unit size surely also have an impact on camera body card reader, I used to be a software engineer and am very interested by your post.

I am gonna digg this further and try to do serious testings. If it only improves the card reading on my PC, I don't care, I'm fast enough ATM with an USB 3.0 card reader, but if it improves camera sequential write on the cards, it's a HUGE information we should all share !

Great subject, I'll give you feedback ASAP

Bruno.
03-29-2016, 10:55 AM   #4
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QuoteOriginally posted by nomadkng Quote
The only drawback is wasted space..
I realised that very quickly when I tried a 32MByte AU size - it halved the card's capacity. Going down to 4MByte dropped the capacity by a little over 5% (1800+ to 1700+). Since I never get anywhere near that number of images on a card I stopped caring.

---------- Post added 03-29-16 at 10:59 AM ----------

QuoteOriginally posted by bygp Quote
but if it improves camera sequential write on the cards
If there was any improvement it was marginal - I didn't notice anything. Importing the files on the PC was a bit quicker, but then I'm still using USB 2

Cheers

03-29-2016, 11:20 AM - 1 Like   #5
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tests in progress on a 16 Gb SDHC class 10, I can already tell that there is definetly an impact on camera write speed :
recording 20 RAW with a 16 Mb AUS takes 25s
recording 20 RAW with a 256 Kb AUS takes 30s
There is certanly an optimum AUS corresponding to each camera model and SD manager (Hard and soft)

---------- Post added 03-29-16 at 11:40 AM ----------

QuoteOriginally posted by bygp Quote
tests in progress on a 16 Gb SDHC class 10, I can already tell that there is definetly an impact on camera write speed :
recording 20 RAW with a 16 Mb AUS takes 25s
recording 20 RAW with a 256 Kb AUS takes 30s
There is certanly an optimum AUS corresponding to each camera model and SD manager (Hard and soft)
AWESOME !

With my K5-II performing these tests (always using same card, same 20 shots in a row...)

With an AUS of 1 Mb recording 20 RAW took only 12s !!!!

this is not a joke, AUS of SDHC cards have a great impact on camera write speed on the card ! Enjoy

I'll keep this 1 Mb AUS for all my cards from now on. There could be an even better size but being 2x faster is already awesome.

(notice that the format action made by the camera is only a quick file system install with main directories, it erases nothing, only acting on the MFT)

Last edited by bygp; 03-29-2016 at 12:16 PM.
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