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My backup is taking forever

This user wonders why his backup is taking so long to complete. Search400.com expert Ken Graap advises.

I'm trying to backup one directory in the IFS, containing about 500,000 files, totaling about 30 GB. Backing up this directory on a LT03 drive with 10 Mbps should be possible in less then one hour; however it takes around four hours to complete. The backup runs right after an IPL, with no users logged on yet. Is there a way to speed this up?

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I have experienced the same issue on my systems. On my baby i5/520 (1 processor) using an internal 6384 tape drive, I'm only able to backup about 155,000 IFS objects an hour.

On my larger AS/400 730 (8 processors) using an external 3590-B11 tape drive, I'm only able to backup about 165,000 IFS objects an hour... really not that big of a difference!

The IFS backup performance isn't tied to how fast your tape drive is. It may be a little more dependent on how fast your system is. However, mostly it is dependent on how many objects there are to save. There is a certain amount of processing overhead involved in getting each IFS object ready to be saved to a tape device. In the case of an IFS backup this is magnified even more because there are usually "many small" objects as opposed to "fewer large" objects.

If you were able to run your IFS save in a "restricted state" you might see some improvement due to the fact that the system doesn't have to worry about object locking. Short of that, there isn't a lot more that can currently be done to speed up a save of the IFS file system.

USER FEEDBACK TO THIS EXPERT Q&A

  • I suspect that the writer did not do his math on this particular problem. What was stated was that the writer wanted to backup 30GB using an Ultrium 3 over a 10Mbps link.

    The theoretical maximum throughput (per hour) that can be put over a 10Mbps link is: 10 X 3600 = 36,000 BITS per hour NOT Bytes per hour

    To get the theoretical maximum number of Bytes per hour we have to divide by 8

    Thus 36,000/8 = 4,500 BYTES per hour

    So in getting the backup done in 3-4 hours is really quite realistic. — Graeme Gates

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This was last published in July 2005

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