Hello, Note: btape does not spool -- it writes directly to the tape. When it is writing random data, you may find that your CPU is maxed out.
The speeds you see are quite reasonable in my opinion. It is unusual that one will reach the theoretical maximum speed. I recommend that you stick with 512KB for all your tape drives because using higher values such as 2MB you are likely to experience higher tape error rates -- though these days with LTO-6 drives, you may be able to get away with 1M write sizes. Personally, I would be reluctant to try larger sizes. Best regards, Kern On 27.11.2015 14:43, Christoph Litauer wrote: > Dear bacula users, > > I recently recognized that my tape drives do not perform as expected. Neither > while used with bacula nor native with dd. I did many performance tests in > the meantime but could not figure out the reason. So may I ask in this group > what typical write speeds you have with your tape drives? > > I tested LTO6 (IBM Ultrium HH6) and LTO4 (Ultrium 4-SCSI). Both are part of > two libraries connected via SAS to a LSI SAS3801E-controller. The host system > runs SLES12. > I used btape and dd for writing. > I figured out the best writing performance with blocksize 512KB (LTO4) resp. > 2MB (LTO6). Both drives with compression on. > > LTO4 best performance (writing zeros): 115 MB/s > LTO4 worst performance (random data): 71.58 MB/s > > LTO6 best performance (zeros): 153 MB/s > LTO6 worst performance (random): 58 MB/s > > Disabling compression does not change the maximum speed. In this case writing > zeros is the same as writing random date (expected). > > According to Wikipedia, theoretical speed should be > LTO4: 240 resp. 120MB/s > LTO6: 400 resp. 160MB/s > > Any ideas welcome! Thanks in advance! > > -- > Kind regards > Christoph > _________________________________________ > Christoph Litauer > Uni Koblenz, Computing Centre, Office A 022 > Postfach 201602, 56016 Koblenz > Fon: +49 261 287-1311, Fax: -100 1311 > > > > > ------------------------------------------------------------------------------ > _______________________________________________ > Bacula-users mailing list > Bacula-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/bacula-users > ------------------------------------------------------------------------------ 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
