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Gilbert, > To: General Support <address@hidden> > From: Gilbert Sebenste <address@hidden> > Subject: Questions about LDM 6.4 > Organization: NIU > Keywords: 200507242026.j6OKQHjo017074 LDM-6.4 The above message contained the following: > Now that 6.4 is out, I almost wish that it wasn't. :-) I managed to release it the evening of the day before the LDM training-workshop so that I could use the attendees as guinea pigs. :-) The web-pages still aren't up-to-snuff and now I have to answer support-email. :-) Such is life. Please bear with me. > I have questions. From the UNIDATA GFORGE website: > > "Automatic switching between primary and alternate transfer-mode by > downstream LDM-s." > > Suppose I have the following 4 scenarios: > > 1. Site 1 (primary) has bandwidth issues and so is behind in sending me > data (say, HRS). Site 2 (alternate) has no issues and is fine. This > means that my LDM will automatically switch to site 2 for data, assuming, > of course, that I have site 2 as an an alternate feed. That's correct. Make sure that the REQUEST entries for site 1 and site 2 have the same feedtype and pattern. > Question: Can I use more than 1 alternate for a particular feed, Yes. > and how does that work? Just add another entry with the same feedtype and pattern. For any given feedtype/pattern pair, the first entry will be the initial primary one and the other will initially be alternates. This brings up an important point: feedtpe/pattern pairs in REQUEST entries should either be identical to those of other entries or completely disjoint (i.e., feedtype/pattern pairs should never "overlap"). > 2. Site 1's upstream site goes down, so site 1's LDM is up, but since they > didn't specify a working alternate, no data is coming from them. Site 2 > is unaffected because it gets its data from a different upstream source > that is working fine. > > Question: Will the LDM automatically switch to site 2 if I have site 2 > specified as an alternate? Yes. > 3. Site 1 is completely down; it's Internet connection is toast. > Site 2 is fine. Question: Will the LDM switch over to site 2 > automatically if I have site 2 specified as an alternate? Yes. > 4. Site 1 is down; site 2's LDM is up but no data is coming from it, and a > site 3 is fine. Assuming I can specify 2 alternates, will the LDM > automatically switch to site 3, assuming I have a second alternate? Yes. > How many alternates can I have? How many are practical? No limit on the number of alternative, upstream LDM-s is imposed by the LDM system. At some point, however, the bandwidth used by the COMINSOON messages from the alternate sites will exceed the bandwidth used by the primary site. Three or four upstream LDM-s for any given feedtype/pattern pair is probably a reasonable upper-limit. > ******************************************************************************* > Gilbert Sebenste ******** > (My opinions only!) ****** > Staff Meteorologist, Northern Illinois University **** > E-mail: address@hidden *** > web: http://weather.admin.niu.edu ** > Work phone: 815-753-5492 * > ******************************************************************************* Regards, Steve Emmerson > NOTE: All email exchanges with Unidata User Support are recorded in the > Unidata inquiry tracking system and then made publicly available > through the web. If you do not want to have your interactions made > available in this way, you must let us know in each email you send to us.