International linksVideoconferencing System

Caching system

Since mid-February 2000 the second cache service started operating thus achieving the planned configuration. In April the official document was published, CDA0025 - Caching system at CARNet, describing the caching system, providing indications of future development and advising its usage.

Increase in the speed of CARNet international link to 34 Mbps in November did not present any additional burden to the system, but it reduced the so-called hit-rate and the time the document stays in cache as result of increased traffic with unchanged available space on the disk.

At the end of the year, the computer equipment necessary for more efficient distribution of load between the two cache servers was completed.

Numerical data:

The increase of speed of the international link proceeded in three phases:

1st phase (by September 2000)

for the server proxy1

  • number of queries weekly: 11 - 15 million
  • volume of documents weekly: 95 - 105 GB
  • % queries from cache: 40 - 45 %
  • % volume from cache: 30 - 35 %

for the server proxy2

  • number of queries weekly: 5 - 7 million
  • volume of documents weekly: 15 - 24 GB
  • % queries from cache: 20 - 25 %
  • % volume from cache: 30 - 35 %

This is the operating phase until September 2000 with the international link of 4 Mbpss. It may be noted that there is a greater number of queries for proxy1. The servers share the documents thus increasing the overall efficiency of the cache system.

2nd phase (from September to November 2000)

for the server proxy1

  • number of queries weekly: 14 - 30 million
  • volume of documents weekly: 55 - 89 GB
  • % queries from cache: 45 - 47 %
  • % volume from cache: 32 - 37 %

for the server proxy2

  • number of queries weekly: 5 - 7 million
  • volume of documents weekly: 14 - 22 GB
  • % queries from cache: 27 - 30 %
  • % volume from cache: 32 - 35%

    This was the period from September to November 2000 when the CARNet international link was jammed. A reduction in traffic volume may be noted as well as increase in the number of queries, due to the fact that smaller documents passed more easily through the jammed network. Lower traffic increased the share of volume served from cache.

3rd phase (since November 2000)

for the server proxy1

  • number of queries weekly: 11 - 18 million
  • volume of documents weekly: 130 - 150 GB
  • % queries from cache: 45 %
  • % volume from cache: 20 - 25 %

for the server proxy2

  • number of queries weekly: 5 - 10 million
  • volume of documents weekly: 30 - 32 GB
  • % queries from cache: 20 - 26 %
  • % volume from cache: 26 - 30 %

This is the phase in which the speed of the international link was increased to 34 Mb by the end of the year. For faster throughput of documents, the average stay of an object in cache was reduced, and therefore also the utilisation of cache This refers particularly to the volume utilisation which is more sensitive since cache system deals faster with bigger documents.

 


© 2001 Croatian Academic and Research Network - CARNet
All rightes reserved

Adjusted for Internet Exploreru 5.x in size 800x600
DiP: CWM 2001