On Tuesday 21 February 2006 21:30, Wolfgang Denk wrote: > In message <[EMAIL PROTECTED]> you wrote: > > C) You run multiple jobs in parallel and want to keep jobs together on > > tape (to allow much faster restores, usually). > > How exactly is this working, especially when the spool size is > smaller then each of the backups? > > Let's say I have 3 jobs "A", "B"" and "C" which all use the same > volume and run in paralel; they all write more data to tape than the > spool device can hold. > > I understand all three of them will start simultaneous, filling their > respective spool files. Assume "A" is fastest, and fills it's spool > file up to the maximum size. > > * I guess the SD now starts despooling the spooled data of "A", while > jobs "B" and "C" continue to run? The FD for job "A" is blocked > now? Is this interpretation correct?
Yes. > > * Assume now "B" fills it's spool file. > > * I guess that once despooling for "A" has completed, two things will > happen: (1) the FD for "A" continues to spool new data, and the SD > starts despooling the data of "B". Is this assumption correct? Yes. > > In the end, we will have a tape / some tapes, where the data of the 3 > jobs are interleaved in big blocks of the size of the respective > spool files. Is this correct? Yes. > > > If yes, then how will a restore be much faster compared to a tape > where all "A" data are consecutive, followed by all "B" and then all > "C" data? It will be slower, but perhaps not by a lot. It will likely be much faster than if you simply ran 3 simultaneous jobs without spooling, and the total backup time should be shorter with simultaneous spooling than running one job after another because data transfer from the FDs is simultaneous. > > Best regards, > > Wolfgang Denk ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642 _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
