BIG B vs little b

28 Mar

Bytes or bits. There is an 800% difference so you better get it right. Networking speeds or even your broadband speed is, for now, measured in bits. If you have “6meg” internet that would be 6Mb or 6 Megabits of download bandwidth. A 10/100 router/switch is 10Mb or 100 Megabits. A 10/100 router can generally transfer your pictures across your LAN at 10MB. Even though its 100Mb of speed its only 10MB of throughput. 100 megabit = 100,000 bits and divide that by 8 to get bytes 12,500 bytes or 12.5MB

The data transfer math works out this way because there are 8 bits in a byte. But you can only really get 10-11MB of throughput because there are usually 2bits of overhead of the TCP/IP or network layer. It’s all the wrapper data in each packet to let the data know where to go and to make sure it got there. Jumbo packets and some other tweaks available in 2003 and by default in server 2008 can alleviate some of this overhead.

Space or file sizes are usually in Bytes. That 3MB mp3 you just downloaded is 3 Megabytes not bits. The 1TB drive is a Terabyte and should have the BIG B notation. A GB has 1024 MB however a Gb only has 1000 Mb, confused yet? Check out this site which also has a handy calculator.

Now it gets rather tricky when you talk about disk throughput to a SAN. Because you tend to converge the networking bits measurements with the storage bytes measurements. It’s a “bit” of a pet peev of mine we engineers refer to these metrics as just “meg” or “gig”. Now, hopefully we can all be sure of what we’re talking about and speak with some BYTES conviction.

One of the best descriptions of bits and bytes

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Posted by on March 28, 2011 in Uncategorized


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