ANSWER:
Do NOT use -streams option. Always run single stream nzbackup. Build for parallelism manually using shell script executing single-stream nzbackup jobs concurrently. This will create a single-stream backupset, which performs fast when recover data with nzrestore.
Advise: upgrade to NPS 7.2 or higher,where both nzbackup and nzrestore have option that perform well. See Netezza: nzbackup & nzrestore on NPS 7.2 post.
EXPLANATION:
As of late 2013, Netezza NPS version 7.0 has parallel nzbackup option -stream, however nzrestore can only be made in a single stream. Empirical test shows that recovery of data using nzrestore linearly degrades with increase of parallelism in source backupset.
TEST CASES:
To obtain the data for this analysis we picked the same size of data. The nzbackup /nzrestore were tested on local backup at netezza host disk and NetBackup Data Domain disk storage. Both disk and network storage showed relatively similar speed performance.
RESULT:
For nzbackup -streams 4 is the "sweet spot" to make create backupset fastest. Seems like a catch, but look further down for nzrestore timing.
For nzrestore, on the other hand, is the fastest when data recovery made from a single-stremed backup set. With increase of parallel -streams in original backupset nzrestore degrades linearly by factor of 2 with each step up in prallelism. Note, nzrestore with 4 streams failed in this test.
NZBACKUP vs. NZRESTORE:
On the same time scale (Axis Y) compare: nzbackup and nzrestor.
Related documentation: The nzbackup command and The nzrestore command
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