Overview

Some customers may benefit by moving files that NMIS reads/writes to very often to a RAM Disk.  We have seen this improve performance on pollers that have shared storage and 2,000+ nodes provisioned.  The concept is that NMIS will be able to read/write to RAM faster than the shared storage.  Most of these files that NMIS touches very often are found in the nmis8/var directory.

Procedure

Step #1 - Determine Space Required

There are two questions that quickly come to mind:

• How big should the RAM disk be?
• How much RAM is available?

Check how much space nmis8/var is currently using; minus the nmis8/var/events directory.  We will keep the nmis8/var/events directory on a hard drive because it contains stateful event history; we don't want to loose these if the server is rebooted. 

[root@TEST var]# pwd
/usr/local/nmis8/var

[root@TEST var]# du -hs
2.6G    .

[root@TEST events]# pwd
/usr/local/nmis8/var/events

[root@TEST events]# du -hs
1.7G    .

In this example we notice that the nmis8/var directory minus the nmis8/var/events directory is approximately 900MB.  It appears that a RAM disk of 1GB would be sufficient.

How much RAM is available?

[root@TEST events]# free
             total       used       free     shared    buffers     cached
Mem:      37016616   25990916   11025700       1796     861860   15379752
-/+ buffers/cache:    9749304   27267312 
Swap:      4169724     558624    3611100 

In the example above there appears to be 11GB of RAM available.