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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 the files that NMIS touches very often are found in the nmis8/var directory.
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Any files written to RAM disk will not survive a reboot. After the server reboots the RAM disk will be empty. Please review this Wikipedia article that addresses tmpfs: |
| Warning |
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This is an advanced configuration technique for large scale deployments with experienced sysadmin. The benefits for small scale deployments would be negligible. |
Procedure
Step #1 - Determine Space Required
There are two questions that quickly come to mind:
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| Info |
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The NMIS Self Test settings may need to be adjusted if the nmis8/var directory is running at a high rate of usage. Look for the following attributes in nmis8/conf/Config.nmis:
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Step #2 - Create the RAM disk
The RAM disk mount point will need to be created. In this example we are using /media/ramdisk; be sure to mind the permissions.
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mount -t tmpfs -o size=1000M tmpfs /media/ramdisk/ mkdir -p /media/ramdisk/nmis8/var ln -s /data/nmis8/var/events /media/ramdisk/nmis8/var /usr/local/nmis8/admin/fixperms.pl |
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When creating the RAM disk the size parameter may be a number expressed with the suffix k, m or g (kilo, mega, and giga). It may also be expressed with the % sign. For example if you'd like to allow the ramdisk to consume up to 25 percent of the available RAM the following technique could be used.
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-t |
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tmpfs |
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-o |
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size=25% |
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tmpfs |
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/media/ramdisk |
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in |
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mind |
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that |
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the |
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ramdisk |
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will |
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not |
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immediately |
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consume |
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the |
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amount |
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of |
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RAM |
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specified. |
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This |
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is |
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the |
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most |
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it |
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will |
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be |
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allowed |
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to |
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consume |
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should |
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it |
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need |
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to. |
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Also |
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keep |
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in |
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mind |
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that |
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if |
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the |
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RAM |
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is |
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oversubscribed |
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the |
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ramdisk |
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could |
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be |
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pushed |
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into |
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swap. |
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If |
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the |
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ramdisk |
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find's |
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itself |
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in |
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swap |
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space |
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it |
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defeats |
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the |
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purpose |
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of |
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this |
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expedition, |
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so |
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do |
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try to avoid this situation. |
| Info | ||
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If you find yourself in a situation where you need to resize the ramdisk on the fly the following method may be useful.
This does not require a reboot and will preserve the files that reside on the ramdisk. |
Use the df command to confirm that the ramdisk was created.
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[root@TEST]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_nmis64-lv_root
16G 11G 4.1G 73% /
tmpfs 5.9G 0 5.9G 0% /dev/shm
/dev/sda1 477M 75M 377M 17% /boot
/dev/mapper/vg_nmis64_data-lv_data
246G 95G 139G 41% /data
/dev/mapper/vg_nmis64-lv_var
20G 10G 8.3G 55% /var
tmpfs 1000M 30M 971M 3% /media/ramdisk |
Step #3 - Disable NMIS
We need to disable NMIS so that it will not attempt to modify the files as we point nmis8/var to the new RAM disk. This is easily accomplished by placing a file called 'NMIS_IS_LOCKED' in the nmis8/conf directly as in the following example.
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When none are found continue
Step #4 - Point nmis8/var at the RAM Disk
Since we are planning to put a sym link in /usr/local/nmis8/ for /var pointing at the new RAM disk; verify that in /usr/local/nmis8/conf/Config.nmis nmis8/var points to /usr/local/nmis8/var. Here's a sample of the directories configuration in that file.
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ln -s /media/ramdisk/nmis8/var/ /usr/local/nmis8 |
Step #5 - Re-enable NMIS
Remove the previously created NMIS lock file.
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[root@TEST]# rm /usr/local/nmis8/conf/NMIS_IS_LOCKED |
Step #6 - Verify
move to the /usr/local/nmis8/var directory and execute a 'df -h .' command. This command should reveal that we are indeed on the ramdisk.
Code Block [root@TEST ~]# cd /usr/local/nmis8/var [root@TEST var]# df -h . Filesystem Size Used Avail Use% Mounted on tmpfs 1000M 30M 971M 3% /media/ramdisk [root@TEST var]#
- Take a look in the /usr/local/nmis8/var directory and confirm that node.json and view.json files have been created.
- Verify that the NMIS GUI is functioning normally.
- Review the nmis8/logs/nmis.log file
- Check the root user mailbox
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