Thanks for the extra information. If we think of 'LSST user' as more than just individuals, but also research teams, or institutions, or other data aggregators, then yes, it is possible that your sci-fi scenario (Case 3) could be very useful, since QoS measures will be important for planning purposes.
However, I believe that even individual astronomers should be warned if their query exceeds some size limit or time-to-delivery criteria. Even if they do not ask for QoS metadata or use it to set limits on their query, nevertheless the DGMS should provide some kind of notification or warning or system administrator-imposed limits on potentially enormous ad hoc queries. For example, one of Jacek's sample queries produces several Petabytes of intermediate results, to be sorted and filtered in order to produce the final end-user result --- the end-user results might be very small, and hence the end-user may have no clue that their query has consumed every byte of storage, every cycle of CPU, and every GBs of bandwidth to generate their little answer. Some QoS measures should be available to intervene in cases like this. - Kirk > Date: Fri, 30 Jun 2006 11:09:12 -0700 > From: Arun Jagatheesan <[EMAIL PROTECTED]> > Subject: RE: [LSST-data] File or image retrieval and access patterns? > To: [EMAIL PROTECTED], "'LSST Data Management'" <[email protected]> > > In the upcoming versions of SRB DGMS, the metadata (LSST schema) could be > part of the SRB system metadata it self. We call it extended MCAT. This > allows queries or file-based requests to have joins on both file-system > metadata and domain-specific metadata. > > Expanding more on this DGMS perspective, I get an additional possibility. I > am thinking loud here... > > Case 0: LSST DB maintains LSST schema. SRB MCAT maintains the DGMS schema of > distributed files in Data Access center and other centers that might join > the LSST data grid collaboration. This will mean the middleware application > will have to query both the schemas to have some infrastructure-dependent > domain queries that need files as output. > > Case 2: LSST schema and DGMS Schema could be maintained in a single SRB > DGMS. Joins are possible during the queries (at this time it's not mature as > we don't have much production users willing to be the guinea pigs). > > Case 3: This is out of the scope of LSST design now as its sci-fi for 2006. > It assumes LSST will have multiple data access centers delivering some part > of the files or the database. LSST schema and DGMS schema are on distributed > databases. SRB can already pick up the closest replica and other things > based on some heuristics. But we can get more aggressive here. Astronomers > could specify infrastructure details like the "time to wait" and "size of > data" they are expecting. Based on this QoS information, the queries could > take advantage of the DGMS data can gather (get) more or less file-based > data that might be distributed at multiple storage systems. > > Cheers, > Arun > > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] > > Sent: Friday, June 30, 2006 10:21 AM > > To: [email protected] > > Subject: Re: [LSST-data] File or image retrieval and access patterns? > > > > Yes, yes, yes. Though I don't see the clear distinction > > between Case 2 and Case 3, unless you mean that the SRB > > metadata are used in Case 3 and the normal LSST DB metadata > > are used in Case 2. > > > > - Kirk > > > > > Date: Fri, 30 Jun 2006 10:04:39 -0700 > > > From: Arun Jagatheesan <[EMAIL PROTECTED]> > > > Subject: [LSST-data] File or image retrieval and access patterns? > > > To: "'LSST Data Management'" <[email protected]> > > > > > > This is a question for which I have been trying to find an > > answer. I > > > would appreciate any friendly enlightenment about the type > > of queries > > > astronomers might have. > > > > > > Will the queries by astronomers be purely database-oriented > > or will it > > > also lead to retrieval of image files from a data grid type > > of system? > > > Case 1: Query the database using only astronomy related > > attributes to > > > get result sets only from database. This is purely RDBMS here - > > > traditional SQL type queries. > > > Case 2: Query the database using only astronomy related > > attributes to > > > get result sets from the database and some files or images. > > (its more > > > DGMS style queries here) Case 3: Query the database using both > > > astronomy related attributes and storage-related attributes to get > > > result sets both from the database and image archive > > > (e.g.) Query on ra, dec etc., and get these metadata, In > > addition get > > > me the associated files only iff they can be retrieved with certain > > > QoS or with a delivery time of these much hours. Or... I don't want > > > 5TB of images coming out of this query but I am ok with 100GB. > > > > > > Thanks in advance, > > > Arun > > > ~~~~~~~~~ > > > Luck is what happens when preparation meets opportunity. > > > > > > Arun swaran Jagatheesan > > > http://www.sdsc.edu/~arun/ > > > San Diego Supercomputer Center. > > > (858)822.5452 > > > > > > > -----Original Message----- > > > > From: [EMAIL PROTECTED] > > > > [mailto:[EMAIL PROTECTED] On Behalf Of Jacek Becla > > > > Sent: Thursday, June 29, 2006 9:24 PM > > > > To: LSST Data Management > > > > Subject: [LSST-data] Database telecon Fri Jun 30 > > > > > > > > Keywords: DataAccWG > > > > > > > > Hi all, > > > > > > > > We will have a Database telecon this Friday at 11:00 AM PDT. > > > > > > > > I'd like to go over the latest disk io numbers. > > > > > > > > Here is the latest version: > > > > > > > > > > http://www.slac.stanford.edu/~becla/tmp/lsst_diskIO_estimates_v04.do > > > > c > > > > > > http://www.slac.stanford.edu/~becla/tmp/lsst_diskIO_estimates_v04.xl > > > > s > > > > > > > > > > > > Shortly speaking the numbers looks very reasonable for everything > > > > except two temporal queries, and both have the same problem (see > > > > below) > > > > > > > > Phone number: 866 330 1200 > > > > Pass code: 300 2363 > > > > > > > > Jacek > > > > > > > > ====================== > > > > > > > > Select time series data for given cone: > > > > > > > > SELECT o.objectId, o.ra, o.dec, i.MJD, d.* > > > > FROM Object o, CCDImage i, DIASource d > > > > WHERE o.ra BETWEEN ra1 + cos(decl1)*(0.5) > > > > AND ra1 - cos(decl1)*(0.5) > > > > AND o.decl between decl1 +0.5 and decl1 - 0.5 > > > > AND o.objectId = d.objectId > > > > AND d.ccdImageId = i.ccdImageId > > > > ORDER BY o.objectId, i.MJD ASC > > > > > > > > > > > > Object table: 10 million rows (one partition) > > > > DIASource table: 45 billion rows > > > > CCDImage table: 135 million rows > > > > > > > > > > > > At the moment, if I assume a modest 1% selectivity for > > ra,dec that > > > > gives 10K rows from Object table. > > > > > > > > Join with DIASource (5 DIASources per star) gives 50K rows, then > > > > join with CCDImage (assuming 10K DIASources per > > > > CCDImage) gives 50*10^12 rows. That is over a petabyte, which now > > > > needs to be sorted, then for each row we need to fetch full > > > > DIASource row.... > > > > > > > > > > > > _______________________________________________ > > > > LSST-data mailing list > > > > [email protected] > > > > http://www.lsstmail.org/mailman/listinfo/lsst-data > > > > > > > > > > _______________________________________________ > > > LSST-data mailing list > > > [email protected] > > > http://www.lsstmail.org/mailman/listinfo/lsst-data > > > > -------------------------------------------------------------- > > --------------- > > Dr. Kirk D. Borne > > NASA Goddard Space Flight Center, SSDOO Program Manager, QSS > > Group Inc. > > and George Mason University, Associate Research Professor, > > College of Science <mailto:[EMAIL PROTECTED]> Tel. > > +1-301-286-0696 Fax: 301-286-1771 > > Staff page: http://rings.gsfc.nasa.gov/~borne/ > > US Virtual Observatory: http://www.us-vo.org/ Large Synoptic > > Survey Telescope: http://www.lssto.org/ > > > > _______________________________________________ > > LSST-data mailing list > > [email protected] > > http://www.lsstmail.org/mailman/listinfo/lsst-data > > ----------------------------------------------------------------------------- Dr. Kirk D. Borne NASA Goddard Space Flight Center, SSDOO Program Manager, QSS Group Inc. and George Mason University, Associate Research Professor, College of Science <mailto:[EMAIL PROTECTED]> Tel. +1-301-286-0696 Fax: 301-286-1771 Staff page: http://rings.gsfc.nasa.gov/~borne/ US Virtual Observatory: http://www.us-vo.org/ Large Synoptic Survey Telescope: http://www.lssto.org/ _______________________________________________ LSST-data mailing list [email protected] http://www.lsstmail.org/mailman/listinfo/lsst-data
