What’s new in vSphere 6.5 Core Storage

Hello from VMworld EMEA in Barcelona. Well, we can finally talk about vSphere 6.5 today. In this post, I want to highlight a number of new and enhanced features that you will find in vSphere 6.5 related to core storage. I am not going to discuss Virtual SAN (VSAN), Virtual Volumes (VVols) or I/O Filter enhancements (VAIO) specifically in this post, although you will no doubt see some new features tie directly into the latter. Instead, I want to talk about those features that are specific to core storage.

New mclock I/O Scheduler in vSphere 5.5 – Some details

My colleague Duncan wrote a post relatively recently around the new mclock I/O scheduler which VMware introduced in vSphere 5.5. He also mentioned some caveats with the new scheduler, especially around the I/O size (32K) used with the IOPS setting, which may lead to some unexpected behaviour. As Duncan mentioned, the reason for introducing the new scheduler is primarily to provide a better I/O scheduling mechanism that allows for limits, shares and reservations. Unfortunately, we didn’t do a very good job of announcing this change in I/O scheduling, or documenting the behaviour, and it has led to a number of…

Does Storage DRS work with Adaptive Queuing?

Many of you will be aware that Storage DRS uses Storage I/O Control (SIOC) for load balancing based on I/O metrics. However a statement in one of our white papers has raised a few questions recently with both our customers and partners. The statement is as follows: “Queue depth throttling is not compatible with Storage DRS”. (pg.34) from  http://www.vmware.com/pdf/Perf_Best_Practices_vSphere5.5.pdf. This assertion led many to believe that Storage DRS would not work well with Adaptive Queuing (AQ), another of VMware’s queue depth throttling mechanisms. However internally, many felt that this wasn’t a true statement, but some work was needed to verify…

Adaptive Queueing vs. Storage I/O Control

This post is to look at two different technologies available in vSphere to manage the queue depth on your ESXi host(s). A queue determines how many outstanding I/Os can be sent to a disk. In the case of vSphere environments, where many hosts can be doing I/O to the same shared disk device, it can be helpful to throttle the LUN queue depth from time to time when congestion arises. In this post, we will compare and contrast Adaptive Queues with Storage I/O Control (SIOC).

vSphere 5.1 Storage Enhancements – Part 8: Storage I/O Control

Storage I/O Control (SIOC) was initially introduced in vSphere 4.1 to provide I/O prioritization of virtual machines running on a cluster of ESXi hosts that had access to  shared storage.  It extended the familiar constructs of shares and limits, which existed for CPU and memory, to address storage utilization through a dynamic allocation of I/O queue slots across a cluster of ESXi servers. The purpose of SIOC is to address the ‘noisy neighbour’ problem, i.e. a low priority virtual machine impacting other higher priority virtual machines due to the nature of the application and its I/O running in that low…