[RFC 004] Operation Review Comment 4

Review of DAP2 operational experience:

NASA's Earth Science Data Systems Standards Process Group (SPG) is considering the Data Access Protocol, Version 2, (DAP2) for adoption as a community standard.  This is the second review of DAP2, this one focusing on its operation experience.� The questions below are provided to guide your feedback. You only need to answer questions applicable to you.  Please send comments to ese�rfc�004@spg.gsfc.nasa.gov.�

1. Describe in a sentence or two your overall operational experience related to DAP2 (e.g., scientific analysis; science users, server operation; database management; or data translation, etc).� What kinds of DAP2 systems do you have experience with?� (e.g., OPeNDAP netCDF server, OPeNDAP HDF server, OPeNDAP Matlab Toolkit, Ferret, GrADS, and etc).
1. How long have you been using DAP2 operationally?

Since August 2003

2. What types of applications do you use DAP2 systems for?� Are the DAP2 systems applicable to your applications? (e.g., Do they work well with the data types and data manipulations in your application?)��
1. How many of your applications use DAP2? THREE
2. Note:� these are application SERVERS.� The OpeDNAP provides requests form many clients as you know�..

                                                              i.      Total number of applications:� OPeNDAP-G (a grid enabled opendap via GLobus---test mode only not operational); GDS and LAS thru GDS

                                                             ii.      Percentage of applications 75%

Note: we also have direct http access and traditional FTP

3. Why do you choose to use DAP2 systems over other systems for your applications?
1. What alternative technologies did you consider?

WCS and OGC.�� But they are next.� OPeNDAP currently fails when it comes to georectification of most satellite data when intercomparing with say gridded data. Thus we are installing OGC type WCS>�

4. Are the DAP2 systems easy to use?� (e.g., Is it hard to learn how to use DAP2 systems?)
1. How has the use of DAP2 affected your user support workload?

Greatly.�� Curently, again, from a Data Provider aspect- NCDC/NOMADS provides a significant portion of ALL binary data via this project alone:� 4TB/ 1 million downloads per month!

5. Does the performance of the DAP2 systems you have experienced meet your requirements?� (e.g., Does it take a long time to access data in DAP2 systems?)
1. Have your bandwidth issues changed since you have been using DAP2 systems? (e.g., Have you seen increased bandwidth requirements because of increased data access or DAP2 overhead, decreased bandwidth requirements because of reduced data volume from subsetting, no impact on bandwidth because of low usage?)

No- but we are moving toward increasing to VERY high bandwidth (Lambda or equiv) to service satellitemodel and Radar data via OpeNDAP and WCS/OGC etc.

6. What operational challenges do the DAP2 systems present? (e.g., Does it require advanced processing power, large amounts of memory, complex configuration, etc.? Are the systems easy to deploy and maintain?)
1. How has the use of DAP2 affected your systems administration workload?

OpeNDAP uses the array index while WCS uses spatial reference coordinates to access the data. WCS way of access to data can ensure the co-registration of data from multiple source/servers, which is very important to multi-source data integration and model/satellite data comparison. The OpeNDAP access cannot ensure that I belive.

7. How well do the DAP2 systems scale to large numbers of simultaneous users, or to large datasets?
1. How much data does your DAP2 system handle in a typical month?

                                                               i.      Total data volume: about 100Gb/month

                                                            ii.      Total number of data files:� 250K/month

                                                            iii.      Percentage of data volume: 20%

                                                          iv.      Percentage of data files 20% (of all data accessed under NOMADS)

8. Can you provide information on user statistics of your DAP2 systems?�
1. How many users does your DAP2 system handle in a typical month? About 300

                                                               i.      Total number of DAP2 users since 2003: 2000

                                                            ii.      Percentage of your overall users: since 2003: 20% but growing�.

2. Of the feedback you have received from your users on DAP2, what percentage is positive and what is negative?

Most is clearly positive.� The only drawback is when users either don�t get it, or when they just want �all the data�.�

3. How have the user statistics changed over time?

See http://nomads.ncdc.noaa.gov/stats/gds/metrics.html for yourself.� GLenn