I have this weird issue with a backup library and ArcServe 11.5. I have a graphics department, working with their own server. Quite often, the have to backup their data to tapes. On the hardware side, they've got the HP MSL2024 tape library with two LTO3 tape devices - and LTO3 tapes. As a backup software, they are using ArcServe 11.5 SP4.
Now, quite often (if not all the time) the data written on tapes is way under LTO 3 tape capacity of 400GB minimum (800GB with 2:1 compression). This recent job could be used as an example (log attached). Out of tape's capacity of 400GB, only 276GB are actually written, before ArcServe requests next tape in sequence. I have disabled file estimation so that ArcServe would write up until the real end of the tape, to no avail.
Any ideas? I've been battling with this for quite a while now. I've even sent the library for a checkup and it returned clean. I often perform head cleaning (last one done yesterday).