On Saturday 25 November 2006 12:13, Peter Crighton wrote: > On Fri, 24 Nov 2006 18:01:27 -0500, you wrote: > > >Did you use a blank tape when you tested bacula for the first time? > > > >If not this is your problem. I do not believe the block size can be > >changed once there is data on the tape. > > > >you can fix this by rewinding the tape and writing an eof at the beginning > >of the tape using > > > >mt -f /dev/nst0 rewind > >mt -f /dev/nst0 weof > > > >then I believe bacula can use the tape and set the block size. > > Tried that - no difference. > > I tried using mt setblk to set the block size and all values I tried > other than 512 gave an error. I suspect that the only valid block size > is 512.
In one sense you are right, the buffer size must be a multiple of 512, but any tape drive that requires all blocks to be written as 512 bytes should be immediately thrown out as it will never perform well on Unix systems, and will be even worse with Bacula which gains a lot of efficiency by blocking, and there is a certain overhead in blocking, which becomes important with small block sizes like 512 bytes, but is insignificant in 64K blocks. I don't believe this is the case for you i.e. I see no reason the tape drive will not accept blocks of larger than 512 byets. It is just a matter of getting all the blocking factors correct. I would be *very* surprised if you cannot use a minimum buffer size of 32K or more. > > Also tried mt -f /dev/nst0 stsetoptions no-blklimits scsi2logical that > I found suggested on a web page, but again no improvement. > > I tried tar cvf /dev/nst0 file, with a 32MB file and the tape drive > ran continuously for 40s, which is about 800kb/s. Read the tape back with dd, which should allow you to determine the block size that tar used. In fact, if you do an strace on tar, you will see *exactly* what it is doing, and you can simply duplicate it in Bacula. It is possible, but I will be very surprised if it is writing in 512 byte chunks. > > Although btape runs the tape drive in a "bursty" mode, will bacula in > fact run it in a continuous write mode or does it use it exactly like > btape? Not having completed the testing of the tape drive I am not > sure how bacula will actually write. > -- > > Peter Crighton > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys - and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > Bacula-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/bacula-users > ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Bacula-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/bacula-users
