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General discussion on using the Kognitio Analytical Platform.
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v8 multi-headed backup not much faster than single-headed

by markc » Fri May 16, 2014 11:42 am

I used to use multi-headed backups to reduce the backup time with version 7. With two APs running the backup I noticed a big benefit.

Upgrading a number of systems to version 8 saw the single-headed backup go much faster than it did in version 7. Typically between 5 and 10 times as fast as the version 7 backup.

However, the version 8 multi-headed backup is only marginally quicker than the version 8 single-headed backup.

Is this to be expected? If so, why?
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Re: v8 multi-headed backup not much faster than single-heade

by markc » Fri May 16, 2014 11:44 am

The dominant part of most backups is compression of the data.

In version 7 this occurred on the client (i.e. the AP in the case being discussed). So doing multi-headed backup added more APs, which meant more cores compressing data, and hence the backup would speed up.

With version 8, the compression occurs in the server in parallel across all nodes. So now using a multi-headed backup won't speed up the compression, and hence won't have much of a benefit for the overall performance of backup.

In general it isn't worth using multi-headed backup with version 8 because it will simply introduce more complexity with backup and restore without giving any significant benefits. One possible reason for doing it would be if a single AP did not have enough disk space for the backup, but in that situation you would be best advised to increase the AP disk space.
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