Slow backup throughput / speed (79317)

Date: 05/07
Affected NV Version: All
OS Version: All
Plugin version: N/A
Application version: N/A

Description: Backups appear to be going too slowly to tape drive

Symptoms: No particular error messages, just slow backups
 

There are many factors that could be involved in slower then expected backups. There are a couple of parameters that can be adjusted within NetVault to see if they may help.

One is to enter NetVault's Device Manager. While the tape drive is idle, right click on it and select Configure. From the screen that comes up select the performance tab. You will see a box that says "Amount of memory to assign for transfer buffers (kb)". The default is 257;
you can increase this to 64M + 1K (65537) for each of your tape drives to see if this helps.

You can go as high as the amount of cache buffers built into the tape drive itself before experiencing diminishing returns. As for the other boxes, always leave number of media read and write blocks set to 1. Changing these numbers can cause data integrity problems.

The next thing you can try (but is not highly recommended) is to go to the configuration tab. If you are backing up mostly larger files, it may help to increase the Blocksize from 32 to 64. In order to test this change, you will need to run a backup where NetVault formats a blank tape, or else the new parameter will not take effect.

WARNING: All drive certification and tests with NetVault Software is done at a 32K Blocksize. Changing this to anything different, you do so at your own risk. You should consult with your tape drive manufacturer about this change, and also make several backup and restore tests until you are convinced it is safe to make the change.

As stated above other factors do affects the performance of a backup job and mostly it is outside Netvault. if the above Netvault configuration does not significantly improves the performance then this confirm it environement related. Determining the exact cause of the bottleneck is not straight forward as it requires many tests. The following is few examples of causes for slow backup performance.

1 - Network - data transferring accross client and target device is simply not robust enough. If server and/or clients have multiple IP addresses be sure Preferred and Barred are set in Network Manager

2- Network - packet being dropped regularly

3- Reading from source is slow

4- Device writing may be slow - modern tape drives tend to be faster but even they can be slow if they are not in good state and writing to bad media.

5- Type and size of files. It is usually easier and lot faster for devices to backup larger file contrary to numerous files.

6- Type of backup - encrypted backup tend to be slower.

BakBone SFDC Solution Number: 00002221