fbackup and frecover

[Sagar Sirdesai]

There is requirement to backup the someFS on a HP-UX11.11. I plan to use fbackup and I've created a graph as below

i /back/data7
i /back/data6
i /back/data5
i /back/data4
i /back/data3

I've a few Queries while specifying the tape device do I need to specify no rewind tape device file like /dev/rnt1mn . Please let me know which tape device file will provide the best performance.

Also I would I know the sequence in which the fbackup has copied the data on tape . I mean does it follow sequence specified in the graph file.

Please advice

Sagar

[James R. Ferguson · Accepted solution]

Hi Sagar:

You should use a rewind tape device file like '/dev/rmt/0m'. Do *not* use a no-rewind device.

The graph, along with any include and/or exclude specifications, is sorted by 'fbackup' before the actual backup begins. This determines the order of files and directories on the tape. This is really immaterial, since by design, the 'fbackup'/frecover' utility writes tape fast search marks and checkpoints to be able to rapidly scan forward to find and recover any particular file or files.

The performance you see with 'fbackup' and 'frecover' is based on the parameters contained in the file defined by the '-c config' file argument (or a default one if no specification is made).

Start with a configuration file that looks like:

blocksperrecord 4096
records 64
checkpointfreq 4096
readerprocesses 6
maxretries 5
retrylimit 5000000
maxvoluses 200
filesperfsm 2000

The manpages for 'fbackup(1M)' document the default settings which is what you will get in the *absence* of an explicily defined set.

These parameters are recorded onto the actual backup tape and are thus used for a 'frecover' session too.

Checkpoint records allow the salvage of a backup when a bad tape spot is detected, since the records contain information about the file being backed up. The 'filesperfsm' parameter controls the frequency with which Fast Search Marks (FSM) are written. Both checkpoint and FSM records affect performance. FSMs take a tape drive out of streaming mode thereby adding to backup time. Conversely, however, FSMs improve the time it take to recover a file from tape.

In general, if your backup consists of a high proportion of small files, increase the value for 'filesperfsm'. If your backup consists of a high proportion of large files, then decrease the 'filesperfsm' value.

Sadly, 'fbackup' is deprecated at 11.31 and is scheduled to vanish in some release thereafter. 'frecover' will continue to be supported for archive retrieval for some longer period.

Regards!

...JRF...

[Sagar Sirdesai]

Thanks James,
What I understand now is I need keep a track how the the file/dirs are backed up.

When I need recover using frecover I just need to specify the directot or file name and the freocer will serach for that particualr file or directory and restore it.

Sagar

[Sagar Sirdesai]

Thanks James,
What I understand now is I need not keep a track how the the file/dirs are backed up.

When I need recover using frecover I just need to specify the directot or file name and the freocer will serach for that particualr file or directory and restore it.

Sagar

[James R. Ferguson]

Hi (again) Sagar:

> What I understand now is I need not keep a track how the the file/dirs are backed up.

Correct. You can use 'frecover' to list the index of files written to the archive using the '-I' option. This is very fast since the index is written to the beginning of the archive. However, since the volume index is created at the start of an 'fbackup' session it is possible that it contains entries that are not actually in the archive because they were removed from the system prior to their copy. You can read the entire 'fbackup' archive in a verification-only mode, using the '-N' switch for no-recovery. This will give a correct accounting of the archive contents while actually reading the archive.

> When I need recover using frecover I just need to specify the directot or file name and the freocer will serach for that particualr file or directory and restore it.

Yes, you use a graph file with includes and/or excludes for your 'frecover' session to select exactly what you want recovered. You can simply specify small numbers of files or paths without a formal graph file by using the '-i' option and argument on the command line, too. see the 'frecover' manpages for more information.

Regards!

...JRF...

[Sagar Sirdesai]

Thanks James