NetWorker Index Hints

There's a few common questions we get asked from time to time about NetWorker indices. Here are the answers to some regular questions.

How much space will my indices take up?

EMC suggests that regular indices will occupy 160 bytes (on average) per file that is backed up and browsable. That lets you get some fairly accurate index sizing. Consider for instance a client with 5 million files on it. If this gets daily incremental backups with weekly full backups that are kept for 6 weeks, and monthly full backups kept for 12 months, with a 5% daily change in files, the index sizing will look like this:

  1. Fulls: 6 x 160 x 5,000,000 12 x 160 x 5,000,000
  2. Incrementals: 6 x 6 x (5,000,000 x 0.05) x 160

This gives a total size of 13.4GB occupied space for indices for this server. (EMC support articles suggest that you should add around another 20% to these calculations for NDMP indices.)

Does NetWorker compare files against the index during backup?

A really common misconception is that NetWorker, when doing an incremental backup, walks the filesystem on the client and the index on the server simultaneously, comparing files to index details. This is not the case.

When NetWorker initiates an incremental backup, it supplies the date of the last successful backup to the client process. At this point, the client walks the filesystem looking for files that have changed since the date provided by the server.

Will NetWorker backup the index of a decommissioned client?

No. In order for NetWorker to backup (or recover) the index of a client, the client must be part of an active group. If it is not, or if the client has been deleted completely from NetWorker, the index directory for the client will not be backed up.