Data Services Newsletter

Volume 3 : No 3 : September 2001

Organization of Data Holdings at the IRIS DMC

Data flows into the DMC from a variety of sources and are archived. This article doesn’t intend to describe the process of archiving but, instead, outline the nature of how our various filesystems are managed and updated. It is helpful to users to understand the fundamental differences in the various data products which are now on-line and readily available in near-real time. This can be useful in determining which data are appropriate for their specific application. (For more about how data requests are handled, see this previous DMS Newsletter article.)

Data holdings at the IRIS DMC
Figure 1: Data holdings at the IRIS DMC.

Data Where are the data stored?
BUD SEED Data coming through the BUD system (details) lives on its own machine. (Some timeseries data can eventually be migrated into the permanent archive.) This real time data can be accessed through the BUD Web interface until it is quality controlled and moved onto the near-line system where it is accessed using any of the DMS’s standard request tools. (Some BUD data receives no further QC and can be archived “as is.”)

NOTE: SEED data that comes into the DMC on tape (not through the BUD) goes through a similar process as the electronic transfers but the archiving process is not automated.
SPYDER® SPYDER® data are managed separately and it stays separate until the data have been replaced by quality-controlled data and converted to FARM volumes.
FARM FARM products are created from quality controlled data that is in the near-line (tape-based) archive and stored with the SPYDER® data, eventually replacing the SPYDER® products.
Assembled data sets Assembled data sets are non-SEED formatted data that come to the DMC on tape (or some other media). Because they are not in SEED format, the timeseries information cannot be loaded into the near-line archive. Instead, a tape image is stored on the archive system. This image can be copied back to a tape, a CD, or to an FTP directory for pickup. (The majority of these data are active-source PASSCAL experiments or special aftershock surveys, for example.)

by Tim Ahern (IRIS Data Management Center)

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