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Terminology, Speeds, Etc
By Matt | October 6, 2007
Bits, Bytes, and Capitals…
Although these seem to get interchanged often, and (except for confusing bits and bytes) don’t make a huge difference…we should try and use the correct, precise language.
Bit is short for Binary digIT, and represents an on(1) or off(0).
A bit is abbreviated with a lowercase b.
A Byte is 8 bits.
A byte is abbreviated with a uppercase B.
Lowercase prefixes, such as k and m, represent multiples of 1000
Uppercase prefixes, such as K, M, G, and T represent multiples of 1024
The differentiation between k and K, etc, is effectively deprecated. The proper replacements, still not as commonly used as capitalization, are to use and “i” — Ki, Mi, Gi, etc. GiB is pronounced “gibibyte” and stands for gig binary bytes. In such a nomenclature both lower case and capital letters without the ”i” stand for powers of 10 and not mulitples of 1024.
This means, for example, a MB is not 1000 KB, but instead 1024 KB.
A common networking term is Mbps — which is 1024*1024 bits per second. This is 1,048,576 bits per second, or dividing by 8 yields a speed of 131,072 Bytes, or 128KBps.
Usually network speeds are expressed in bits per second, while file sizes are quoted in Kilo, Mega, or Giga bytes as appropriate for the file size.
Network Speed & Files…
The general rule with ethernet is you can utilize a maximum of 80% of the bandwidth. If you have plenty of bandwidth and files are still moving slowly, look for another issue such as disk contention.
The following calculations are done assuming the 80% efficiency factor and rounded off:
T-1 1.54Mbps = 154KB/s, 9.25MB/m, 540MB/h
10Mbps LAN = 1MB/s, 60MB/m, 3.5GB/h
T-3 45Mbps = 4.5MB/s, 270MB/m, 15.8GB/h
100Mbps = 10MB/s, 600MB/m, 35GB/h
1Gbps = 100MB/s, 6GB/m, 351GB/h
A handy online File Transfer Speed calculator
To achieveve 1Gbps performance, or anything really much over 400Mbps, you need to have network cards with “TOE” (TCP Offload Engine) capability which is enabled. Otherwise too much CPU time is taken processing network stuff at those speeds.
USB Speed & Files…
1.0 — 1.5Mbps
1.1 — 12Mbps
2.0 — 480Mbps
So unless you’re on a 10Mbps network…
It’s faster to use a USB 2.0 computer and transfer files via the network then suffer a USB 1.1 drive!
Cat 3/5/6 Wiring:
A ton of pin-outs is available at: http://www.hardwarebook.info/
IP Subnetting
Private Subnets:
10.0.0.0 — 10.255.255.255, mask 10.0.0.0/8
172.16.0.0 — 172.31.255.255 mask 172.16.0.0/12
192.168.0.0 — 192.168.255.255 mask 192.168.0.0/16
CIDR & Masks:
| CIDR | Class | Hosts | Mask |
|---|---|---|---|
| /32 | 1/256 C | 1 | 255.255.255.255 |
| /31 | 1/128 C | 2 | 255.255.255.254 |
| /30 | 1/64 C | 4 | 255.255.255.252 |
| /29 | 1/32 C | 8 | 255.255.255.248 |
| /28 | 1/16 C | 16 | 255.255.255.240 |
| /27 | 1/8 C | 32 | 255.255.255.224 |
| /26 | 1/4 C | 64 | 255.255.255.192 |
| /25 | 1/2 C | 128 | 255.255.255.128 |
| /24 | 1 C | 256 | 255.255.255.000 |
| /23 | 2 C | 512 | 255.255.254.000 |
| /22 | 4 C | 1024 | 255.255.252.000 |
| /21 | 8 C | 2048 | 255.255.248.000 |
| /20 | 16 C | 4096 | 255.255.240.000 |
| /19 | 32 C | 8192 | 255.255.224.000 |
| /18 | 64 C | 16384 | 255.255.192.000 |
| /17 | 128 C | 32768 | 255.255.128.000 |
| /16 | 256 C, 1 B | 65536 | 255.255.000.000 |
| /15 | 512 C, 2 B | 131072 | 255.254.000.000 |
| /14 | 1024 C, 4 B | 262144 | 255.252.000.000 |
| /13 | 2048 C, 8 B | 524288 | 255.248.000.000 |
| /12 | 4096 C, 16 B | 1048576 | 255.240.000.000 |
| /11 | 8192 C, 32 B | 2097152 | 255.224.000.000 |
| /10 | 16384 C, 64 B | 4194304 | 255.192.000.000 |
| /9 | 32768 C, 128B | 8388608 | 255.128.000.000 |
| /8 | 65536 C, 256B, 1 A | 16777216 | 255.000.000.000 |
| /7 | 131072 C, 512B, 2 A | 33554432 | 254.000.000.000 |
| /6 | 262144 C, 1024 B, 4 A | 67108864 | 252.000.000.000 |
| /5 | 524288 C, 2048 B, 8 A | 134217728 | 248.000.000.000 |
| /4 | 1048576 C, 4096 B, 16 A | 268435456 | 240.000.000.000 |
| /3 | 2097152 C, 8192 B, 32 A | 536870912 | 224.000.000.000 |
| /2 | 4194304 C, 16384 B, 64 A | 1073741824 | 192.000.000.000 |
| /1 | 8388608 C, 32768 B, 128 A | 2147483648 | 128.000.000.000 |
This is a guide…remember to factor in network & computer speeds, compression, encryption when designing a solution.
Also, small files make a dramatically longer backup. Single, big files like Databases are most efficient streaming data.
| Tape Type | Native Capacity (GB) | Transfer Rate (GB/hr) |
| LTO 3 | 400 | 80 |
| LTO 2 | 200 | 40 |
| LTO 1 | 100 | 20 |
| SDLT 160/320 | 160 | 57.6 |
| SDLT 110/220 | 110 | 39.6 |
| DLT 40/80 | 40 | 21.6 |
| DLT 20/40 | 20 | 5.6 |
| AIT 100/200 | 100 | 43.2 |
| AIT 50/100 | 50 | 21.6 |
| AIT 35/70 | 35 | 14.4 |
| AIT 35/70 IDE | 35 | 14 |
| DAT 20/40 (DDS-4) | 20 | 8.4 |
| DAT 12/24 (DDS-3) | 12 | 3.6 |
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