Forum Discussion

elanmbx's avatar
elanmbx
Level 6
8 years ago

5230: Excessive swap usage?

Just wanted to see what others' experiences might be regarding swap usage on their appliances - I have one *very* busy appliance which recently was exhibiting performance issues... and upon investigation I saw that there was over 30GB of swap in use (of 64GB configured).

Upon investigation of my other appliances, I do see swap in use, but it is quite a bit lower (10-12GB).

I'm actually pretty surprised that there is *any* reported swap in use, since there always seems to be a bit of free memory reported on each of the appliances.

5230 Media Servers, Appliance Version 3.0

  • eduncan's avatar
    eduncan
    Level 5
    8 years ago

    It would require closer monitoring but at some point your appliance is running low and memory and seeking swap.

    Too many concurrent jobs can cause that.  Also maybe you have a job that requires more memory than the standard job.

    See if you can identify why it is getting exhausted what is running and maybe reduce the number of concurrent operations.

    Otherwise engage NetBackup support for a closer investigation.

    • eduncan's avatar
      eduncan
      Level 5
      8 years ago

      I forgot to mention you can look into vm.swappiness value on the appliance.

      https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Performance_Tuning_Guide/s-memory-tunables.html

      swappiness

      A value from 0 to 100 which controls the degree to which the system favors anonymous memory or the page cache. A high value improves file-system performance, while aggressively swapping less active processes out of physical memory. A low value avoids swapping processes out of memory, which usually decreases latency, at the cost of I/O performance. The default value is 60.
       
      A low swappiness value is recommended for database workloads. For example, for Oracle databases, Red Hat recommends a swappiness value of 10.

       

    • elanmbx's avatar
      elanmbx
      Level 6
      8 years ago

      Like I said - all of my appliances are using swap space.  The average seems to be around 10GB of swap space that is reported being used.

      I've been keeping an eye on them, with a focus on the swap usage.  The busy appliance that had the 30+ GB of use is pretty steady right now at 12GB.  I'm going to see if at any point that starts to head up...

      • sdo's avatar
        sdo
        Moderator
        8 years ago

        elanmbx could you tell us exactly what and exactly how you are measuring, so that we can also feedback any figures, and compare apples with apples.  Thank you.