Understand the basic concepts of vFlash in VMware vSphere 6 and how it can be used to improve performance.
- [Voiceover] In this video, I'll explain vFlash and how you can use it to improve the performance of your virtual machines. We'll talk about the architecture behind vFlash and the system requirements that exist. Solid State and Flash storage provide space that we can use to store data. These technologies do not have any moving parts and outperform traditional spinning disks. Over time, the cost of these high performance storage components has come down. And they're now an affordable option that we can add to our ESXI hosts. vFlash is a vSphere feature that we can use to take advantage of this high speed storage technology.
vFlash was introduced in vSphere 5.5 as a feature called Flash Read Cache. Virtual Hardware Version 10 was also released with vSphere 5.5. When VMware releases new versions of vSphere, they're normally accompanied by a new virtual hardware version. This allows virtual machines to take advantage of new features and resource limits. In order to enable vFlash on a virtual machine, it must be Virtual Hardware Version 10 or later. vFlash is configured on individual virtual machine disks. The vFlash capacity provides a high performance read cache.
Frequently accessed data on the virtual disk is also stored on the vFlash resource, which exists on a flash device within the EXSi hosts. This means that often a virtual machine will read data directly from vFlash instead of the storage array, which greatly improves performance. The other big performance benefit comes from the local nature of vFlash data. The vFlash resources are installed locally on the EXSi hosts. This means that when virtual machines access this data, they do not need to traverse a storage network.
This not only improves performance, but it also reduces traffic on the storage network. Before you purchase any SSD or flash resources, you should make sure that they're compatible with vFlash. A list of supported devices can be found in the VMware Compatibility Guide. vFlash is compatible with VMDKs that are stored on NFS or VMFS data storage. It is not compatible with VSAN or Virtual Volumes. vFlash is also incompatible with Fault Tolerance. If you need 100% uptime for a critical, virtual machine, you may choose to use Fault Tolerance.
vFlash works best on virtual machines with consistent data sets. If a virtual machine frequently accesses the same data repeatedly, it is a good candidate for vFlash. This frequently accessed data will most likely be stored in vFlash and will perform very well. If the virtual machine data is constantly changing, vFlash performance will suffer. What happens if the flash resource fails? These failures do not create an outage for the virtual machine. However, the performance of the virtual machine may suffer because the read cache is no longer available.
So how does vFlash know what data to cache? Well it starts out by caching everything that the virtual machine reads until the cache is 90% full. And then it will begin an eviction process. The eviction process will start discarding data that is least frequently read. And as time goes on, the eviction process will ensure that the most frequently read data is present on vFlash Read Cache.
VMware Certified Instructor Rick Crisci provides an overview of vSphere resource controls—shares, limits, and reservations—and their impact on performance and VSWP file size. Rick explains exactly what happens when virtual machines compete for resources, the role of swap files, and how resource controls help automate allocation.
In chapter 2, Rick shows how to manage performance with resource pools, including child pools. He explains the impact a reservation has on resource pools, and includes a demo on creating and configuring a resource pool. Chapter 3 is an overview of the vFlash architecture for leveraging SSD resources. Watch this chapter to learn how to configure vFlash reservations and to assign a reservation to a VM.
Note: This course maps to the Administer and Manage vSphere 6.x Resources domain of the vSphere Certified Professional 6—Data Center Virtualization (VCP6DCV) exam.
- Allocating memory and CPU
- Using ESXTOP
- Configuring reservations, limits, and shares
- Managing performance with resource pools
- Creating child and tiered resource pools
- Leveraging SSD resources with vFlash