Quick Way to Evaluate Linux Server Load To Determine if Upgrade is Needed?

by TechJaz   Last Updated October 11, 2019 16:00 PM

I've got mission critical apps running on my VDS. We're not experiencing any visible lag issues from the user perspective. However I want to be cognizant about when it's time to upgrade. The network load is low and I don't believe there are any disk I/O (it's SSD RAID-5) or memory bottlenecks. It's a KVM instance with 2 dedicated CPUs (why Ramnode calls it a VDS and not VPS) and 8GB RAM running Centos 7 and a SugarCRM install with no more than 6 simultaneous users and 6 low-traffic Wordpress sites.

So in my opinion the main thing I need to watch is CPU usage. Below is header from top command and I've set a cron event to output CPU usage every 15 minutes. I know this is a 2-cpu system and it is dedicated CPU because it's a VDS on VPS. Is your opinion the same looking at the CPU usage in 15 minute increments below that the CPU load is well within tolerance for the current instance and no posing any significant bottle neck? I tend to focus on the second and third numbers showing 5-minute and 15-minute average as have a burst in the 1-minute is not as concerning, or do you think the VDS is nearing it's limit on CPU? My thinking is as long as 5-minute and 15-minute numbers are not exceeding 3.0 then I am fine? I know there are other tools (like vmstat) and others that I can use but for a simple quick check, is this information good enough to just check for obvious server overload?

1.81 1.35 1.61 13/448 4598
0.86 1.20 1.33 12/454 10227 
3.88 1.65 1.14 11/480 15646 
4.40 2.90 1.80 7/460 21584 
1.76 1.37 1.49 14/443 27245 
2.01 1.42 1.28 12/454 32656 
3.98 1.86 1.36 9/465 5890 
4.18 2.81 1.86 7/455 11599 
2.57 1.68 1.58 7/453 16947 
1.59 1.43 1.45 10/443 22651

top - 11:54:39 up 20 days, 16:03, 2 users, load average: 0.67, 1.12, 1.31 Tasks: 156 total, 3 running, 153 sleeping, 0 stopped, 0 zombie %Cpu(s): 41.9 us, 6.5 sy, 0.0 ni, 48.4 id, 3.2 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem : 8010484 total, 613228 free, 2096892 used, 5300364 buff/cache KiB Swap: 1048572 total, 72816 free, 975756 used. 4995584 avail Mem



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