[Bug-tar] Problem spanning multiple (removable) hard disks

[Wayne Liu]

While testing a SCSI drive system which takes removable hard disk as cartridges, I ran into some interesting behavior of tar:

 

1. In my tests, I have my SCSI drive under /dev/sda. All the removable hard disk cartridges are formatted with a single partition, which show up under /dev/sda1 when inserted, and is mounted under /dev/media/disk.

2.  I tested creating an archive by writing to a tar file on the partition (also tested writing directly to the partition handle) using the following commands:
    > "tar -Mcvf /media/disk/tar_file_name file-list"

After filling out the cartridge, tar prompted for the second & third volumes, etc. Then I was able to ejected the cartridge and inserted a new one (which is auto-mounted at the same point), and tar completed the archive without error. However, when I tried to restore the archive, tar gives an error when the second cartridge is inserted "tar: This volume is out of sequence".  But the headers of the second volume (using “tar tvf ….”) looks fine. I tested different file systems (ext2, ext3, and FAT32), all have the same problem. Interestingly, FAT16 worked!

 

3. If I specify a tape-length which is smaller than my removable disk size using the “-L N” option, then tar can create and restore the archive without any error.

 

It seems that without the “-L N” option, tar cannot handle the end of disk partitions in these newer file systems. Can anybody tell me what’s causing it? (May be it’s because that a hard disk drive doesn’t give early warning as a tape drive?). Is it a bug that needs to be fixed?

 

 

Thanks in advance!

Wayne

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