Re: [tlug] The meaning of B in Kb/secs?

["Jonathan Q" <jq@example.com>]

On 8/13/2002, "Jean-Christian Imbeault" <jean_christian@example.com>
wrote:

>Ok, silly question but I've always been confused when it comes to data
>transfer rates (be in hard drives or ethernet connections) wether the B
mean
>bits or bytes?

That depends on whether it's a hard drive or a network connection.
Networks speeds are measured in bits/second, disk (and other mass
storage device) transfer rates are measured in bytes/second.

>>From my apache server config-status I get:
>
>48.9 requests/sec - 413.7 kB/second - 8.5 kB/request
>
>Is that kilobits or kilobytes?

That ought to be documented somewhere, and it would be a good idea to look
at it to be sure, unless someone else pops up with a citation here. 
However, if they follow the convention (many people don't, and many others
don't even know about it, such that these days the convention is honored as
much in the breech as in the observance) they are talking about bytes.  The
convention is lower-case b = bits, upper-case B = Bytes.

>The reason I ask is that the pipe to my server at a data center is a
>100MB/sec pipe (which I assumes means 100 Megabytes/sec)

bits/sec

>If I really am using only 0.417% then I'll think to switching to a 10MB
line
>instead.

You're under-utilizing your line, but not as much as you think.

Let's assume theoretical maximums here (something you will never touch
in real life):

100,000,000 b/sec is the speed of your line.

Your transfer rate from Apache is 413,700 B/sec, or 3,309,600 b/sec,
or about 3.3% of your line capacity.

However, is this your average transfer rate?  If so, you're looking  at the
wrong numbers.  When assessing your bandwidth needs, you need to look at
your peak transfer rates.  If your peak is, for example, 8,000,000
bits/sec, you're still with in the capacity of a 10 megabit line with
capacity to spare.

If your peak is 12,000,000 bits/second, you're over the capacity of a 10
megabit line, however, if the cost savings is significant, you might be
willing to accept a touch of /. effect once in a while.  Another option in
that situation is to ask your colo provider if they can provide bandwidth
in 10 megabit increments.  If so, you could get 20 megabits if 10 megabits
isn't enough.

Other considerations are that what Apache is telling you is not your total
traffic, it's only your total Apache traffic.  If you're running an FTP
server or have a lot of interactive sessions, IRC, etc., this also needs to
be considered.  The numbers you need to look at for determining how big of
a pipe you need are your interface statistics, not your Apache
statistics.

Your provider may well already be tracking this info with MRTG or Cricket
and could tell you where to view it.  If not, you could run one of them on
your server for that purpose yourself.  Your provider tracks it at their
router interface, whereas you would, of course, track it at your Ethernet
interface.

Jonathan