A little scary.

The consequences of inadvertently swapping sdb5 and sda5 could
be catastrophic.

Dump can write to a regular file which is probably a bit safer at least while testing.
eg:

$ sudo dump 0uaf /export/backups/root.dump /dev/sda5

Also, disk devices are often read-only for group ‘disk‘ so that running a dump as an unprivileged user in-group ‘disk‘ is another possible precaution.

eg for user backup:disk something like:

$ sudo -u backup -g disk dump 0uaf /export/backups/root.dump /dev/sda5