> That's not how hardware compression for tapes work. You write > blocks of, say, 1 GB to to tape, and depending on how good that > data can be compressed the length of tape (usually, the length > of the track(s)) used vary. You really can't know how much > data fits on a tape before measuring it, and if hardware > compression is on your results areonly valid for your test data. > So, one solution would be using of software compression? I guess Bacula allows it? Then, the amount of data written to the tape (drive) would be known exactly, and this would propably make it possible to know exactly how much tape there is left.
Anyway, for rough estimates one propably could trust the hardware compression to work with almost constant factor too, as long as the environment (including the type of data) remains constant. Information on the amount of data written to tape drive is available in the logs, but it's beyond my knowledge how it possibly could be used to automate the recycling decision. Actually, it would be nice to be able to define "mark volume full at the end of job if xxx gigabytes has been appended". This could propably be done with an external script, that was called after the finished backup? However, I find calling external scripts to manipulate the database more error-prone compared to built-in features. Am I just too paranoid? If one tape could normally store eg. 5-6 backups, this actually has little practical value -a constant number of backups before recycling is propably enough, considering the required tolerance. But if a single tape could handle eg. 25-30 backups, this could become more valuable -it might allow eg. one extra month to be available before recycling. -- TiN ------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
