[PLUG] Setting up dirvish backup: I/O errors

[Rich Shepard]

I have a 2T external hard drive connected via USB to the desktop. It's
formatted ext4. It has four directories: /salmo-root/, /salmo-home/,
/salmo-opt/, and /salmo-data/. In /etc/fstab/ it's entered as:
/dev/sdc1        /mnt/backup      ext4        defaults         1   2

/etc/divish/master.conf has been written (mimics that of the old server).

Following the HOWTO-DIRVISH I mounted /dev/sdc1 on /mnt/backup (fdisk
identified that drive as sdc; sda is the SSD boot drive and sdb is the hard
disk with everything else.

Navigating to /mnt/backup/salmo-data/ (since that's the first alphabetically
in the list of directories) I made the dirvish/ directory and created
default.conf containing:

client: root at salmo.appl-ecosys.com
tree: /data
xdev: 0
index: gzip

Saved and navigated to /salmo-home/. Created the dirvish subdirectory and
the default.conf file. But when I tried saving that file I was told:
error opening file: Input/output error

#ls
reading directory '.': Input/output error

Now I cannot list files or directories anywhere on that backup drive:

[root at salmo /mnt/backup/salmo-opt/dirvish]# ls
ls: reading directory '.': Input/output error
[root at salmo /mnt/backup/salmo-opt/dirvish]# cd ..
[root at salmo /mnt/backup/salmo-opt]# ls
ls: reading directory '.': Input/output error
[root at salmo /mnt/backup/salmo-opt]# cd ..
[root at salmo /mnt/backup]# ls
ls: reading directory '.': Input/output error
[root at salmo /mnt/backup]#

If I umount and remount the drive I can add one default.conf to a backup
subdirectory.

What might I have done incorrectly?

Rich