>>>>> On Sun, 23 Dec 2018 13:00:00 +1000, Adam Nielsen said: > > I had not thought to try the btape program, thank you for pointing that > out. Combined with the "tapestat" program which prints throughput in > MB/sec, it has revealed some interesting behaviour and the probable > cause of the issue. > > btape: btape.c:1074-0 Test with random data, should give the minimum > throughput. > btape: btape.c:911-0 Begin writing 8 files of 1.073 GB with raw blocks of > 1048576 bytes. > +++ > btape: btape.c:612-0 Wrote 1 EOF to "peapod-d1" > (/dev/tape/by-id/scsi-350014380125815e1-nst) > btape: btape.c:411-0 Volume bytes=1.073 GB. Write rate = 82.59 MB/s > ++ > btape: btape.c:612-0 Wrote 1 EOF to "peapod-d1" > (/dev/tape/by-id/scsi-350014380125815e1-nst) > btape: btape.c:411-0 Volume bytes=1.073 GB. Write rate = 67.10 MB/s > ++ > btape: btape.c:612-0 Wrote 1 EOF to "peapod-d1" > (/dev/tape/by-id/scsi-350014380125815e1-nst) > btape: btape.c:411-0 Volume bytes=1.073 GB. Write rate = 71.58 MB/s > ++ > btape: btape.c:612-0 Wrote 1 EOF to "peapod-d1" > (/dev/tape/by-id/scsi-350014380125815e1-nst) > btape: btape.c:411-0 Volume bytes=1.073 GB. Write rate = 67.10 MB/s > [...] > btape: btape.c:385-0 Total Volume bytes=8.589 GB. Total Write rate = 70.40 > MB/s > > At each point where btape says it wrote an EOF mark, the throughput > drops to zero, the drive stops, backtracks, then starts again with the > next file. The throughput btape reports for the second and subsequent > files is slower, because it is including the tape backtrack time in the > overall calculation. > > So it looks like when Bacula/btape writes an EOF mark, this causes the > buffers to completely flush out and the drive then runs out of data > and is forced to stop and shoe-shine. > > To confirm this, instead of writing 8x 1GB files as above, I tried > writing 1x 8GB file, and sure enough there is no shoe-shining: > > btape: btape.c:1074-0 Test with random data, should give the minimum > throughput. > btape: btape.c:911-0 Begin writing 1 files of 8.589 GB with raw blocks of > 1048576 bytes. > +++++++++++++++++ > btape: btape.c:612-0 Wrote 1 EOF to "peapod-d1" > (/dev/tape/by-id/scsi-350014380125815e1-nst) > btape: btape.c:411-0 Volume bytes=8.589 GB. Write rate = 110.1 MB/s > btape: btape.c:385-0 Total Volume bytes=8.589 GB. Total Write rate = 110.1 > MB/s > > I've had a look through the storage daemon options but I can't see > anything relevant.
Try increasing MaximumFileSize for the device in bacula-sd.conf. It defaults to 1000000000. __Martin _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
