Quantum 6-01376-05 User Manual

  StorNext File System Tuning

The Metadata Network

StorNext File System Tuning Guide

7

The Metadata Network

As with any client/server protocol, SNFS performance is subject to the 

limitations of the underlying network. Therefore, it is recommended that 

you use a dedicated Metadata Network to avoid contention with other 

network traffic. Either 100BaseT or 1000BaseT is required, but for a 

dedicated Metadata Network there is usually no benefit from using 

1000BaseT over 100BaseT. Neither TCP offload nor are jumbo frames 

required.
It is best practice to have all SNFS clients directly attached to the same 

network switch as the MDC systems. Any routing required for metadata 

traffic will incur additional latency that impacts performance. 
It is critical to ensure that 

 settings are correct, as this will 

severely impact performance. Most of the time 

is the correct 

setting. Some managed switches allow setting 

, such as 

, which disables 

 and requires the host to be set 

exactly the same. However, performance is severely impacted if the 

settings do not match between switch and host. For example, if the switch 

is set to

 auto-detect

 but the host is set to 

, you will observe a 

high error rate and extremely poor performance. On Linux the 

 

tool can be very useful to investigate and adjust 

 settings.

It can be useful to use a tool like 

 to help verify the Metadata 

Network performance characteristics. For example, if 

netperf -t TCP_RR 

reports less than 15,000 transactions per second capacity, a performance 

penalty may be incurred.

The Metadata Controller System

The CPU and memory power of the MDC System are important 

performance factors, as well as the number of file systems hosted per 

system. In order to ensure fast response time it is necessary to use 

dedicated systems, limit the number of file systems hosted per system 

(maximum 8), and have an adequate CPU and memory.