Re: [tlug] Slightly OT: HD transfer rates vs Internet access speed

["Stephen J. Turnbull" <stephen@example.com>]

>>>>> "Jean-Christian" == Jean-Christian Imbeault <jean_christian@example.com> writes:

    Jean-Christian> (If this is pointless babble or completely OT just
    Jean-Christian> ignore ....)

It's neither.

    Jean-Christian> Newer Mode 5 Ultra ATA EIDE drives offer a maximum
    Jean-Christian> data transfer rate of 100 MB/s. This would seem to
    Jean-Christian> mean that for a web server it would be pointless
    Jean-Christian> to get an Internet connection faster than 100 MB/s
    Jean-Christian> since the server cannot possily read and provide
    Jean-Christian> data from the HD at a rate equal to the Internet
    Jean-Christian> connection.

B0Ti is correct in pointing out cache.  At present on the machine I'm
writing this on, I have 256MB, of which about 46MB (say 20%) is
allocated to cache.  Things like "/robots.txt", "/index.html",
"/errors/404.html" etc will reside there pretty much permanently.

Other considerations.

1.  Other applications, such as mail and your local users browsing the
web.

2.  Internet overhead (TCP/IP headers, etc).

3.  Distributed web servers.

4.  I don't serve any pages like /dev/hda1.  ;-)  That is, most pages
are small, thus HTTP overhead (both directions count against the page
served, unless you're getting a lot of PUT activity, unusual) will be
significant (though not so great).  The HTTP overhead is all generated
by the CPU, not read from disk.

5.  Many pages will be generated by memory-resident CGIs, with no disk
access at all.  /cgi-bin/pi.py will be limited only by your CPU speed ;-).

6.  Many disk accesses are likely (both for security and performance
reasons) to be offloaded onto separate file or database servers.  You
could imagine a diskless webserver!


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