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PAX - Headers

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Occasional Contributor

PAX - Headers

Hi, currently we have switched to using pax_enh from ftio to perform system backups. However, I can't seem to find any info on creating a header on the tape made with pax_enh to include the index of files on the tape.

Has anyone run into this, and found a solution?

Thank you,

Acclaimed Contributor

Re: PAX - Headers

I don't think pax has that. That's only in fbackup or an enterprise strength backup utility.
Occasional Contributor

Re: PAX - Headers

Would you have any alternatives to use other then pax_enh, to support large file sizes that would also include tape headers for HPUX?
Honored Contributor

Re: PAX - Headers

> Would you have any alternatives to use other then pax_enh, to support large file sizes that would also include tape headers for HPUX?

Only fbackup will do this, and it does it at a much higher performance level than pax. Although fbackup is being phased out (a dubious decision), it works fine for all supported versions of 11i with the caveat that 11.31 tapes are not backward compatible. It handles any file size (multi-TB) on HP-UX.

The reason that fbackup has much better performance is that it can run 6 reader processes to keep the tape running at full speed. Today's tape drives (LTO3, LTO4 and LTO5) are MUCH FASTER than simple (JBOD) disk drives, requiring as much as 100 to 200 MBytes/sec to keep them at full speed. Most disks are hard pressed to keep data flowing faster than 30-75 Mbytes/sec. Disk arrays can virtualize multiple disks so that multiple data streams will exceed a single disk's data rate.

In addition to creating a complete table of contents at the front of the tape, for multiple tapes, the same TOC is written to each tape with a marker indicating what data starts on each tape. Thus, a 4 tape backup can recover a single file in just a few minutes by inserting the LAST tape, then following the instructions from frecover to insert the correct tape. frecover also skips files at high speed due to search marks recorded on the tape.

There are other features not found in simple Unix tools like pax, cpio or tar. The performance increase goes up with the tape speed. Many users see a 2x to 5x speed increase over pax or tar with LTO3 tapes. To take advantage of fbackup's speed, always use this config file /etc/fbackup.conf:

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

Then backup your files with:

fbackup -i / -v -c /etc/fabckup.conf -f /dev/rmt/0m

(substitute / with the directory(s) you want to backup, and 0m for the tape drive you have.

After the backup is complete, use this command to check the header:

frecover -V - -f /dev/rmt/0m

and this command to make a copy of all the filenames on the tape:

frecover -I - -f /dev/rmt/0m

Going forward, you will probably want to switch to Data Protector (not free) to enjoy all the features of fbackup/frecover after HP-UX version 11.31.

Bill Hassell, sysadmin
Occasional Contributor

Re: PAX - Headers

Thank you for your very informative reply, I am looking into Data Protector now and will discuss it with my colleagues.