Formatted 4GB card question - General Chat - CHDK Forum
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Formatted 4GB card question

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Offline Mirfak

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Formatted 4GB card question
« on: 29 / August / 2008, 15:23:58 »
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I was wondering if there were issues in practice regarding wasted space with the large 64K allocation unit.  It means that, on average, 32K space is wasted for every file written to the card.  Is this concern warranted?
« Last Edit: 29 / August / 2008, 15:25:34 by Mirfak »
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Offline PhyrePhoX

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Re: Formatted 4GB card question
« Reply #1 on: 29 / August / 2008, 15:29:23 »
not really, since you only have huge files (at least 3 megs per jpg), not many small ones.
i might be wrong though ;)
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Offline Mirfak

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Re: Formatted 4GB card question
« Reply #2 on: 29 / August / 2008, 16:50:52 »
My concern was mostly the accumulated waste over multiple files.  However, a quick calculation shows that the average space wasted for a card with 900 jpegs is only about 28M, or the equivalent of 9-10 jpegs.

Thanks for the response!
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Offline true

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Re: Formatted 4GB card question
« Reply #3 on: 29 / August / 2008, 18:54:15 »
Do some simple math. :)

If you shoot only Fine quality JPEG on an A720IS, it estimates around 1800 files.

Assuming the worst case that only one byte in each 64kb is written to, an absolute maximum amount of wasted space is around ~110MB, or about 3% of formatted space.

In practice, you won't see nearly this high. If you shoot RAW, or shoot higher quality like Superfine, you'll have less files, and less wasted space.

3%? It's not really an issue for camera use patterns.
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Offline littlejohn

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Re: Formatted 4GB card question
« Reply #4 on: 30 / August / 2008, 01:29:47 »
Compared to the convenience of CHDK, a little waste of space in SD card doesn't really matter.
On the other hand, setting the block size to 64k would result in a faster access time. :)
Or you can try dual-partition on your 4G-card, then a small FAT is enough, the rest can be formatted to FAT32.
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Offline Howdy

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Re: Formatted 4GB card question
« Reply #5 on: 30 / August / 2008, 06:38:52 »
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the rest can be formatted to FAT32

Careful! Some cameras can be much slower accessing FAT32 than FAT16. I would format the card as FAT16 with large allocation unit and then forget about the issue.

If space is a problem, get a 16 GB card and partition it to 2 parts - one tiny for CHDK, the rest for pictures. I use it on PowerShot S5 IS and there is no problem.
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