Comments on: Walking the Workload Tightrope Part Three http://www.linux-mag.com/id/7224/ Open Source, Open Standards Sat, 05 Oct 2013 13:48:18 +0000 hourly 1 http://wordpress.org/?v=3.1 By: fgalan http://www.linux-mag.com/id/7224/#comment-6106 fgalan Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7224/#comment-6106 I agree in the most of the hints... except in combining non-overlapping workloads, that should be considered carefully. Although this technique could optimize the overall workload execution in the virtualized infrastructure, it also penalizes other things. In particular, it breaks application isolation, which is bad from the point of view of faults, maintenance, etc.<br /> <br /> Let me clarify with an example. Consider the same case you mention: a CPU intensive application and a disk intensive application coexisting in the same VM. A single OS hang will break both applications (while if they were separated in the VM, it only comprises one of the applications). In addition, if some maintenance operation is required for either the CPU or the database application (i.e. an OS reboot due to the administrator needs to increase VM assigned RAM), this operation penalizes the other application.<br /> <br /> In summary, consider not only workload efficiency when combining non-overlapping workloads, but also how it impacts application isolation. I agree in the most of the hints… except in combining non-overlapping workloads, that should be considered carefully. Although this technique could optimize the overall workload execution in the virtualized infrastructure, it also penalizes other things. In particular, it breaks application isolation, which is bad from the point of view of faults, maintenance, etc.

Let me clarify with an example. Consider the same case you mention: a CPU intensive application and a disk intensive application coexisting in the same VM. A single OS hang will break both applications (while if they were separated in the VM, it only comprises one of the applications). In addition, if some maintenance operation is required for either the CPU or the database application (i.e. an OS reboot due to the administrator needs to increase VM assigned RAM), this operation penalizes the other application.

In summary, consider not only workload efficiency when combining non-overlapping workloads, but also how it impacts application isolation.

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