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Kibibyte, Kilobyte – The divider 1024 and 1000

What are all these acronyms? What is the difference between MB, MiB and 1000 and 1024 dividers, especially when it comes to hard drive sizes?

The KiB, MiB, TiB style became more widespread known when Ubuntu started using this. It’s called kibibyte, and wikipedia explains it rather well.

This became to be used to differentiate between SI definition where kilo equals 1000, and where as in information technology size is described in powers of 2, ie. 1024. This is also the major differentiation between real and advertised disk space. However, it is also very widespread to use KB, MB to describe KiB or MiB – it’s all about the context knowing which is being used!

You’ve probably been one of those cursing that when you buy a 3TB drive you don’t actually get 3TB? Well, they are not wrong, you are getting 3TB – but not 3TiB. Physical world isn’t restricted in powers of 2, there things are measured as kilo (1000) instead of kibi (1024).

So, 1TiB is actually 1024MiB, which is 1 048 576KiB. 1TB would efficiently be 1 000 000KB. A difference of few percentage. That’s why 1TB drive actually has: 1 000 000 000 000 bytes, which translates to  931.32GiB.

This, is also why we advertise in disk space in GiB & TiB. Same goes for RAM.

To further complicate things, networking actually works in the usual metric standard with 1000 instead of 1024 as divider – and in bits instead of bytes. So 100Mbps becomes 100 000 000 bits per second, which translates to 12 500 000 bytes per second -> 11.92MiB per second. In abbreviation, it’s usually used 11.92MBps to actually describe 11.92MiBps. Sounds complicated?? Fortunately, there isn’t many more of these differences 🙂

Small b stands for bits and big B stands for Bytes. So, when in forums you see people writing 11mbps, they often actually means 11MBps, which means the same as 11MiB/s.

Sidepoint from networking: You never get the full bandwidth, some of it is used for error correction, a quick rule of thumb is that 5% is used in error correction, hence 11.32MBps is pretty much the maximum. You may see 11.6MBps in the real world with short, shielded cabling – putting the minimum error correction “loss” to about 2.5%

aleksi

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