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compressed backup size differ between tape & disk

Mike KutzJun 5 2014 — edited Jun 17 2014

This is out of pure curiosity.

DB 11.2.0.3 EE on OEL 5.6 (64bit) + Adv. Compression

TSM for MML

Both disk and sbt_tape are configured for compressed backupsets

compression algorithm is configured for 'HIGH'

If I backup to disk, it takes 1.5hrs and produces a 10GB backup piece.

If I backup to tape, it takes 5hrs and produces a 27GB backup piece.

Watching "top", it seems like 1 core runs @ 100% with most of that (>90%) being "user" (ie not I/O bound or wait)

(backing up the 10GB backup piece to tape takes <2 min over a 1GigE link)

Has anybody else seen this type of size difference when they do a compressed backup to disk vs tape?

Is this suppose to happen?

Should I be concerned?

Many thanks for any information,

MK

This post has been answered by Mike Kutz on Jun 17 2014
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