On 02/12/15 12:14, Paul Elliott wrote: >> Maximum block size = 2M > > Have you experienced any issues with that block size?
Only when the drives/tapes are dirty and then you get excess errors on all block sizes anyway. Because entire blocks are rewritten if there is an error, "tape waste" goes up, but even with small blocks I've seen 75% of a tape lost to rewrites. You do need to watch those stats and react quickly if they're climbing - where react quickly == put a cleaning tape in the drive asap. Unfortunately Bacula does not lend itself well to such interventions. We had one major incident where a faulty HP LTO5 tape contaminated a drive (beyond the point where a cleaning tape would work). That drive then proceeded to contaminate the next 10 tapes loaded into it and those tapes then cross-contaminated the other drives before we realised what was happening. Tape manufacturer warranties don't cover consequential damages of this type so this can get quite expensive to sort out. (The maintenance agreement on the drives covered it, but it was still highly disruptive) The more general problem is environmental cleanliness. Human skin dust (which is almost all dust in a household or office environemnt) is one of the worst possible contaminants for tapes because it's slightly greasy. Neither standalone or library manufacturers pay any attention to this issue, with non-filtered inlets and enclosure fans invaribly pulling air through the tape mechanisms. If at all possible, tape drives/libraries should be in heavily filtered environments with as few humans around as possible. I strongly recommend against having them in a server room if you can avoid it. A dedicated closet/room is better and ideally your data safe should be colocated with the library (less handling, less risk). I'd recommend active air filtration (scrubbers) and humidity control if you can get it too. The cleaner the environment, the fewer problems you'll have with the drives. As an example of this: When building work was performed in the server room, despite the library being partitioned off with plastic sheeting, every single drive failed within 6 weeks. >> These are local-specific (my spool has up to 20 jobs feeding into 280GB >> of >> available space) and if you have more space/fewer jobs I'd consider >> bumping the Job spool size anything up to 100GB >> Maximum Spool Size = 120G >> Maximum Job Spool Size = 30G > > What's the advantage of the maximum job spool size setting? These are tunables. Job Spool size is effectively the chunk size of the backups on tape - in this case, 30GB. This allows various jobs to interleave on the tape drive without impacting restore speeds badly. Maximum Spool Size is a device limit. It's set to try and run out of spool space. It's not healthy to get up to the limit as jobs will start spooling, run out of disk space and them despool. If that chunk is only a few tens of MB then you affect overall throughouts. Setting both is a matter of compromise. I'd prefer to use 50-100GB Job spool size but my spool area is too small to allow that without risking runing out of disk space. I've also got a run-before script which tests spool space and holds the job if it's over 70% (sleep on failure, then loop and test again). We get better overall throughput this way than by letting jobs fight over the spool. The same script checks the number of jobs actually running on the client and imposes a hard limit on the number of full backups in progress. On the fileservers (200-800TB apiece) it's set to 15 incremental/differentials and 6 fulls(we backup in 1Tb segments), because more than that many fulls start affecting both througput and server latencies (again, sleep and loop). Bacula's maximum concurrent jobs settings don't provide enough granularity for our needs. ------------------------------------------------------------------------------ Go from Idea to Many App Stores Faster with Intel(R) XDK Give your users amazing mobile app experiences with Intel(R) XDK. Use one codebase in this all-in-one HTML5 development environment. Design, debug & build mobile apps & 2D/3D high-impact games for multiple OSs. http://pubads.g.doubleclick.net/gampad/clk?id=254741911&iu=/4140 _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
