vSphere Distributed Resource Scheduler (DRS) provides a simple and easy way to manage your cluster resources. DRS works well, out of the box for most vSphere installations.
For cases where more flexibility is desired in how the cluster is managed, DRS provides many options in the form of cluster rules, settings and advanced options.
Often the impact of using rules in a DRS cluster is not very well understood. The settings and advanced options are not very well documented. Imagine if it was possible to play around with rules in your cluster before actually applying them, or changing the DRS migration threshold in your cluster without changing the setting in your live cluster – and yet, be able to visualize the impact of those actions in your cluster?
Introducing – DRS Dump Insight – to help with simple queries regarding DRS behavior, like the following.
- What if I dropped all the affinity rules in my cluster?
- What if I set cluster advanced option “AggressiveCPUActive”?
- What if I changed the DRS migration threshold from 3 to 5?
In an effort to provide a more insightful user experience and to help understand how vSphere DRS works, we recently released a fling: DRS Dump Insight.
DRS Dump Insight is a service portal where users can upload drmdump files and it provides a summary of the DRS run, with a breakup of all the possible moves along with the changes in ESX hosts resource consumption before and after DRS run.
Users can get answers to questions like:
- Why did DRS make a certain recommendation?
- Why is DRS not making any recommendations to balance my cluster?
- What recommendations did DRS drop due to cost/benefit analysis?
- Can I get all the recommendations made by DRS?
DRS Lens provides an alternative UI for a DRS enabled cluster. It gives a simple, yet powerful interface to monitor the cluster real time and provide useful analyses to the users. The UI is comprised of different dashboards in the form of tabs for each cluster being monitored.
One of the questions I was often asked about resource pools (RP) is ‘Expandable reservation’. What is expandable reservation, and why should I care about it? Although it sounds intuitive, it can be easily misunderstood.
To put it simply, a resource pool with ‘expandable reservation’ can expand its reservation by asking more resources from its parent .
The need to expand reservation comes from the increase in reservation demand of its child objects (VMs or resource pools). If the parent resource pool is short of resources, then the parent expands it reservation asking resources from the grand parent.
Let us try to understand this with a simple example. Consider the following RP hierarchy. If RP-4 has to expand its reservation, it requests resources from its parent RP-3 and if RP-3 has to expand resources it eventually requests Root-RP.
Mystery revealed, DRS for VMware vSphere is no more a black box! DRS Doctor will tell you all you need to know about your DRS clusters.
Our latest fling, DRS Doctor, will monitor your DRS clusters for virtual machine and host resource usage data, DRS-recommended migrations, and the reason behind each migration. It also monitors all the cluster-related events, tasks, and cluster balance, and logs all this information into a plain text log file that anyone can read.
Read this blog for more information on how DRS Doctor can monitor and diagnose your clusters.
Download DRS Doctor from our flings site.
Storage I/O Control (SIOC) allows administrators to control the amount of access virtual machines have to the I/O queues on a shared datastore. With this feature, administrators can ensure that a virtual machine running a business-critical application has a higher priority to access the I/O queue than that of other virtual machines sharing the same datastore. In vSphere 4.1, SIOC was supported on VMFS-based datastores that used SAN with iSCSI and Fibre Channel. In vSphere 5, SIOC support has been extended to NFS-based datastores.
Recent tests conducted at VMware Performance Engineering lab studied the following aspects of SIOC:
- The performance impact of SIOC: A fine-grained access management of the I/O queues resulted in a 10% improvement in the response time of the workload used for the tests.
- SIOC’s ability to isolate the performance of applications with a smaller request size: Some applications like Web and media servers use I/O patterns with a large request size (for example, 32K). But some other applications like OLTP databases request smaller I/Os ≤8K. Test findings show that SIOC helped an OLTP database workload to achieve higher performance when sharing the underlying datastore with a workload that used large-sized I/O requests.
- The intelligent prioritization of I/O resources: SIOC monitors virtual machines’ usage of the I/O queue at the host and dynamically redistributes any unutilized queue slots to those virtual machines that need them. Tests show that this process happens consistently and reliably.
For the full paper, see Performance Implications of Storage I/O Control–Enabled NFS Datastores in VMware vSphere 5