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Netbackup 7.5 - Storage Unit Best Practices

Created: 26 Nov 2012 • Updated: 12 Dec 2012 | 2 comments
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I would like to know the recommended storage unit configurations.  We have 16 LTO5 tape drives connected to 3 media servers (server 1 - 4 drives, server 2 - 6 drives, server 3 - 6 drives).  They are all the same density.  Should I create 1 storage unit per media server or should I create multiple storage units per media server and then set max concurrent write drives for each storage unit.  Does anyone know the pros and cons of each and what the best approach is?

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Joseph_TKLee's picture

Max concurrent writing affect restore performance.

4 multiplex is recommanded.


Marianne's picture

One STU per media server since all drives are in the same robot and same density.
I don't see the need or purpose of more than one STU per media server. 

The amount of max concurrent write drives really depends on media server capabilities. 
Do each of these media servers have sufficient physical resources to stream 4 or 6 LTO5 drives simultaneously? How is data received from clients? Network or Fibre Transport?
If network, 1Gb or 10Gb NICs in media servers? Bear in mind that a 1Gb NIC can at best receive data at +- 100MB/sec. This will barely stream 1 LTO5.

This 4-year old White paper is still useful for master/media server requirements: 

To get back to your question about STU config - you need to test various settings. Document results after each change. Test number of concurrent drives in combination with Multiplexing. We have found MPX value of 4 to give good backup and restore performance. Remember to also enable MPX in Policy schedules.
Read up about memory requirements with regards to number of drives, MPX value, SIZE_DATA_BUFFERS, NUMBER_DATA_BUFFERS.

If you back up lots of small files and receive regular requests for a single file restore, then it is best to reduce STU fragment size. We have seen a number 5000 giving good backup and restore performance.

So, in summary - there is no 'one size fits all'. You really need to read all available documentation such as STU config in Admin Guide I, NBU Backup Planning and Performance Tuning Guide, the doc that I've mentioned above, followed by testing in your environment.

Hope this helps.

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