Read Errors

Fewer than 32 read errors on the file system are ignored.

Process Per Reel

Because each reel requires a new process, parent processes for reels that are already written hang around until the entire tape is written.

Operator Intervention

ufsdump requires operator intervention on these conditions: end of volume, end of dump, volume write error, volume open error or disk read error (if there are more than a threshold of 32). In addition to alerting all operators implied by the n option, ufsdump interacts with the operator on ufsdump's control terminal at times when ufsdump can no longer proceed, or if something is grossly wrong. All questions ufsdump poses must be answered by typing yes or no, as appropriate.

Since backing up a disk can involve a lot of time and effort, ufsdump checkpoints at the start of each volume. If writing that volume fails for some reason, ufsdump will, with operator permission, restart itself from the checkpoint after a defective volume has been replaced.

Suggested Dump Schedule

It is vital to perform full, "level 0", dumps at regular intervals. When performing a full dump, bring the machine down to single-user mode using shutdown(8). While preparing for a full dump, it is a good idea to clean the tape drive and heads. Incremental dumps should be performed with the system running in single-user mode.

Incremental dumps allow for convenient backup and recovery of active files on a more frequent basis, with a minimum of media and time. However, there are some tradeoffs. First, the interval between backups should be kept to a minimum (once a day at least). To guard against data loss as a result of a media failure (a rare, but possible occurrence), capture active files on (at least) two sets of dump volumes. Another consideration is the desire to keep unnecessary duplication of files to a minimum to save both operator time and media storage. A third consideration is the ease with which a particular backed-up version of a file can be located and restored. The following four-week schedule offers a reasonable tradeoff between these goals.

              Sun    Mon    Tue    Wed    Thu    Fri


    Week 1:   Full    5      5      5      5      3


    Week 2:           5      5      5      5      3


    Week 3:           5      5      5      5      3


    Week 4:           5      5      5      5      3

Although the Tuesday through Friday incrementals contain "extra copies" of files from Monday, this scheme assures that any file modified during the week can be recovered from the previous day's incremental dump.

Process Priority of ufsdump

ufsdump uses multiple processes to allow it to read from the disk and write to the media concurrently. Due to the way it synchronizes between these processes, any attempt to run dump with a nice (process priority) of `−5' or better will likely make ufsdump run slower instead of faster.

Overlapping Partitions

Most disks contain one or more overlapping slices because slice 2 covers the entire disk. The other slices are of various sizes and usually do not overlap. For example, a common configuration places root on slice 0, swap on slice 1, /opt on slice 5 and /usr on slice 6.

It should be emphasized that ufsdump dumps one ufs file system at a time. Given the above scenario where slice 0 and slice 2 have the same starting offset, executing ufsdump on slice 2 with the intent of dumping the entire disk would instead dump only the root file system on slice 0. To dump the entire disk, the user must dump the file systems on each slice separately.