High Memory Usage. Is this an Issue?

Summary

This article reviews if paging alerts or high memory usage is a problem on the Exinda or not

Overview

Every Exinda appliance has a fixed amount of RAM in it. We also add a fixed amount of SWAP usage to the device in case RAM is completely used. A question generally arises if highly used RAM and partly used SWAP is an issue and if it is performance impacting.

Exinda firmware version 7.0 and above have enhanced performance and monitoring capabilities in them. This requires more RAM than the older versions. It is recommended to have at-least 4GB RAM (minimum) for the device to be functioning well with the new firmware (7.0 and above).

In cases where installed RAM is 4GB and device runs version 7 on it, there are high chances that it will consume the 4GB RAM and start using SWAP (which is meant to be used when RAM is consumed). It can happen on any hardware platform with any amount of RAM, since it depends on the connection rate, processing and work load on the appliance for monitoring flows.

It is recommended that when monitoring memory usage look at trends. Look at the amount of memory being used in the last 7 days, last 30 days or last few months and look at the memory usage in the past few days.
If there is a significant change in trend, as in, if the memory usage has increase significantly, then it is a possibility that
a) Number of users/ hosts have increased in the network (genuine or DDOS)
b) the device requires more memory than before and could be a process mis-behaving causing this.

If the trends look normal, then there is nothing to worry about.

If there is an odd increase, then it is recommended to contact support so that the cause can be determined

High memory usage can
a) Slow down the web access to the Exinda's management interface
b) Slow down report generation
c) Slow down graph display
d) Rarely seen performance (optimization) impact
e) Cause processes to halt, crash or hang up
f) Could cause device to reboot if SWAP is also nearly used
g) It can use bridge link flaps.

Resolution

If the box cannot be upgraded in terms of memory, double check whether there the box is the exact means for the network traffic and operations passing through it. Similarly, if the device is older, if possible, measure the performance differences between v6 and v7 of the firmware; if the v7 performance is notably worse, this is due to the firmware and what it needs. It's been noted that running a v7 firmware on a 2061, 4010 and 4061v1 (stock RAM) can cause notable RAM usage and performance degredation.

Memory can be increased on certain platform by adding more RAM on the appliance. This applies to some of the 'higher' models - 6062, 8062, 10062, 4061 (v1-v3)

In order to do so, it is recommended to contact support to find out if the hardware platform in question is capable of memory increase and to find out how much is required and where to get it from.

Internal Notes

If customer's want to increase RAM on appliances, check out how much RAM can be increased and contact the sales rep for the account to provide them a quote.