Path: senator-bedfellow.mit.edu!bloom-beacon.mit.edu!usc!cs.utexas.edu!swrinde!sdd.hp.com!decwrl!pa.dec.com!reid
From: reid@pa.dec.com (Brian Reid)
Newsgroups: news.groups,news.lists,news.admin.misc,news.lists.ps-maps
Subject: USENET FLOW ANALYSIS for JUL 93: Who stores how much news
Date: 12 Aug 1993 00:53:37 GMT
Organization: DEC Network Systems Laboratory
Lines: 70
Approved: reid@pa.dec.com
Message-ID: <24c4ah$7mv@usenet.pa.dec.com>
NNTP-Posting-Host: torrey.pa.dec.com
Keywords: arbitron, statistics, lifetime
Originator: reid@torrey.pa.dec.com
Xref: senator-bedfellow.mit.edu news.groups:78010 news.lists:2719 news.admin.misc:3852 news.lists.ps-maps:1161

Analysis of stored news articles, JUL 93.

This is an analysis of the contents of /usr/spool/news at the sites reporting
"inpaths" data. The "inpaths" program has been posted in
news.lists.ps-maps,comp.sources.d,news.admin.misc. Please consider installing
and running this program at your site.


Presumed size of overall network:	        97000
Number of sites surveyed:                         441 (0.5%)
Average age of articles kept online:              9.3 days
Average age of disk space used by news:          12.2 days
Average disk space used by news:                208.3 megabytes
Average number of articles stored:              69432
Estimated worldwide disk space used by news        20 terabytes

Distribution of expiration times used
  0-1  	   9  *********
  1-2  	   5  *****
  2-3  	  22  **********************
  3-4  	  16  ****************
  4-5  	  27  ***************************
  5-6  	  30  ******************************
  6-7  	  26  **************************
  7-8  	  31  *******************************
  8-9  	  34  **********************************
  9-10 	  59  ************************************************************
 10-12 	  34  **********************************
 12-14 	  18  ******************
 14-16 	  28  ****************************
 16-18 	  15  ***************
 18-20 	  23  ***********************
 20-25 	  15  ***************
 25-30 	  12  ************
 30-35 	   5  *****
 35-40 	   4  ****
 40-45 	   1  *
 45-50 	  10  **********
 50-75 	   2  **
 75-100	   4  ****
100-125	   3  ***
125-150	   1  *
150-175	   2  **
175-200	   2  **
200-225	   0  
225-250	   1  *
250-275	   0  
275-300	   0  
300-325	   0  
325-350	   0  
350-375	   0  
375-400	   1  *

Notes: 
	The "average disk space used by news" assumes that the host operating
	system allocates disk space in a fixed "chunk size" of about 1000
	bytes. The size of each stored message is rounded up to the next
	multiple of that chunk size. 

	The "average age of articles" is an average counting each article
	equally. The "average age of disk space" is weighted by size.

	The "expiration time" for a site is not necessarily constant. Some
	newsgroups that are considered more valuable are given longer 
	expiration times, while obvious junk is given a shorter expiration
	time. To come up with a single expiration time for a site, we find
	the average age of stored articles and then double it, rounding to
	the nearest integer. If you expire all articles older than 14 days,
	and if the arrival rate is constant, then the average age of 
	articles at your site will be 7 days.