Changes between Version 1 and Version 2 of drmsGeneralAndHMIissue

Timestamp:

04/12/21 15:33:15 (3 years ago)

Author:

niles

Comment:

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drmsGeneralAndHMIissue

@@ -12 +12 @@
 SDO data are organized by '''series''' with a series typically being data from a certain instrument that has been processed in a certain way. Popular series include '''aia.lev1''' (level one AIA data) '''hmi.m_45s''' (HMI 45 second magnetograms) and '''hmi.ic_45s''' (HMI 45 second continuum images).
 
-There is a difference in the way that AIA and HMI data are organized.
+There is a difference in the way that AIA and HMI data are organized. Each AIA image is an item on its own (also, AIA data are actually stored on disk with complete data headers, but still need to go through the export process in order for the data filename to be meaningful). HMI data, however, are bundled together, so that several HMI images together form a the minimum amount of HMI data. This characteristic, that several HMI images are bundled together as a unit, is considered a trait of HMI data.
 
 
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 The second way that data are copied from the JSOC to the remote sites is known as a '''user''' copy. This occurs when a user requests data from a remote site that is not in the remote site buffer of data. In this case, a copy is initiated, and the user who made the request is then obliged to wait while the copy of the data from the JSOC to the remote site takes place, and then wait for the export of the FITS file(s) requested to take place before the download can begin.
 
+For both user and mirror data copies, only a certain number of copies from the JSOC can take place at a certain time. If the limit on the number of copies is reached, then subsequent data copy requests are queued until a copy in process finishes. The intent is to avoid a network bottleneck due to their being too many copies taking place at once.
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+Note that when AIA data is copied to a remote site, only one image needs to be copied to answer a user request. Because of the bundling of HMI images, however, all the images in an HMI bundle may need to be copied to serve out a single HMI image.
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+=== 3.0 Distribution of data served out by series ===
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+The bulk of the SDO data served out is for the AIA level one series. The pie chart below shows a breakdown of the SDO series served out by the NSO remote site for the first quarter of 2021. This is a period during which the system was running normally without other problems, such as storage being offline at the JSOC, or an issue at NSO, or a network outage. Note that the pie chart is based on the count of data items served out, as opposed to the number of bytes delivered. Approximately 80% of requests are for AIA data.
 
 
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