Table Of Contents

FAQs

FAQs

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This appendix answers frequently asked questions.

1. How many NSV engines do I need?

You only need one. That should be enough for hundreds of DSCs. However, for fail-safe and redundancy issues, you might want at least two

2. How many DSCs do I need?

You need one DSC for every site. DSCs come in models that handle 25, 50, or 100 devices. Some sites will have only a router. Others will have both a distribution and access switch, while others may have combinations of those and/or aggregation switches, managed devices, or NAT device. See the "DSC details" section.

3. What are NSVE and DSC hardware and operating system requirements?

This is covered in Installing OverDrive Network Hypervisor, but basically each NSVE and each DSC is a Linux box running CentOS.

4. What options are available for redundancy?

The PostgreSQL database uses a warm standby method with write-ahead logs containing changes to apply to the database. When PostgreSQL runs in archive mode, these files are copied to another location, so they can be used to recover in the event of a failure. The standby is then run in recovery mode, with the archive files copied to it, and then applied to the database. In the event of a failure of the primary, the standby is taken out of recovery mode (by creating a trigger file), and then the standby can take over as the new primary. (A script performs the steps to create the warm standby server.).