Veritas NetBackup™ Appliance Capacity Planning and Performance Tuning Guide
- About this Guide
- Section I. Capacity planning
- Section II. Best Practices
- Section III. Performance tuning
- Section IV. Quick reference to Capacity planning and Performance tuning
Jumbo frame implementation for increased MTU
Jumbo frames are the expression used to describe TCP frames with increased Maximum Transmission Unit - MTU to 9000. They can be very useful in improving throughput for some workloads and even reducing CPU utilization of the appliance.
Note:
Jumbo frames are not covered by IEEE RFI's and are not considered network standard due to which they might not be supported by all network environments
Implementation of Jumbo frames ensures the following performance improvements:
Increased MTU allows for faster transport of data when NetBackup client is sending large streams of data to the appliance, typically in the Media server based deduplication or the AdvancedDisk backup scenario. In these cases significant improvement in the LAN throughput is noticed.
In order for the increased MTU to work, all other network devices in the same segment have to be configured with the same MTU, otherwise MTU will be negotiated down to the lowest MTU configured on the network device connected to the same network segment. This usually means that VLAN has to be created and that both NetBackup Client, all network equipment (switches, routers and other equipment) and the appliance have to be configured with the same MTU size.
Although increased MTU equates to a better throughput the following pointers need to be taken into consideration, prior to implementing Jumbo frames:
NetBackup client based deduplication workload segments and hashes the data on the client and sends a number of smaller packets of data to the appliance. In this case, increased MTU size will not have a positive effect and should be avoided.
Maximum MTU size that should be set is 9000 since this represents a limit of the TCP CRC (Cyclic Redundancy Check). A CRC is a method of checking for errors in data that has been transmitted on a communications link. Although this point is argued, it is without doubt that TCP CRC will have a risk of failing to protect data integrity if MTU is higher.