I've been looking at our backups recently and noticed that the tape throughput is a lot lower when writing lots of small files, so was thinking of tarring those small files up into one big tar file and the writing that to tape instead of the small files directly. (Much like Tar: avoid archiving of files larger than certain size)
However, when I then write this tar file to tape am I going to have problems if there is a tape error during it? I mean, am I going to lose that whole (large) file containing a lot of smaller files, or will I just lose a particular block of that tar file and be able to recover the rest of the files?
Also, how do backup programs like Amanda or Bacula cope with lots of small files? Do they just write the files individually to tape or do they do something like this pre-tarring into larger files which will write faster?
Note : It might just be that our staging disks are too slow, but I'm assuming that small files cause a backup performance problem like this for most people.