Image sizes too big for SD card?

[KPhillisJr]

Hey

This has been already discussed on the forum - I tried finding the link for you but couldn't find it. I'm not an expert BUT it appears that some manufacturers use a GB as exactly 1,000,000,000 bytes while an actual GB has 1,073,741,824 bytes. So a 16GB case would be = 14.9 GB
[someone correct me if I am wrong]

Without getting any further into this I can say that I've had no issues with Samsung SD cards, but did encounter issues with other manufacturers.

This is exactly what is happening. In reality most storage Makers use the following units to size their products...

• 1 terabyte (TB)  = 1000 gigabytes (GB)
  
• 1 gigabyte (GB) = 1000 megabytes ( MB)
  
• 1 megabyte (MB) = 10000 kilobytes (kB)
  
• 1 kilobyte(kb) = 1000 bytes
  

The issue is that the dd image uses the binary representation which has the following conversion table:

• 1 tebibyte (TiB) = 1024 gibibyte (GiB) = about 1099 gigabytes
  
• 1 gibibyte (GiB) = 1024 mebibyte (MiB) = about 1073 megabytes
  
• 1 mebibyte( MiB) = 1024 kibibyte  (KiB ) = about 1048 kilobytes
  
• 1 kibibyte (KiB) = 1024 bytes
  

Using this table, You can see that 99% of the SDCards will probably fail to write disk images under windows since most manufactures use the decimal representation of disk sizes. This means the following sizes will always hold true.

• 8 GiB SDCard image will require approximately 8.6 GB sdcards
  
• 8 GB SDCards will always hold at least 7.45 GiB
  
• 16 GiB SDCards will require at approximately 17.2 GB SDCards
  
• 16 GB SDCards hold about 14.9 GiB.
  
• 32 GiB SDCards Images require about 34.5 GB SDCards
  
• 32 GB SDCards Images require about 29.8 GiB SDCards
  
• 64 GiB SDCard Images require about 68.72 GB SDCards
  
• 64 GB SDCard Images require about 59.6 GiB SDCards.
  

I believe a practical solution would be to correct the actual SDCard Image sizes to the above Bolded lines.