White Papers

In this white paper, Rawlinson Rivera will focus on providing answers to the most frequently asked questions regarding one of the pillar of the software-defined datacenter of VMware – storage. VMware vSphere Flash Read Cache.

• What is vSphere Flash Read Cache VFFS?
• What are the minimum and maximum numbers of hosts required for VMware vSphere Flash Read Cache?
• Is there a way to configure the VFFS for multiple VMware ESXi hosts simultaneously?

Download: VMware vSphere Flash Read Cache 1.0

 

The SEsparse virtual disk format was introduced in VMware vSphere® 5.1 for VMware® Horizon View environments where reclamation of storage space is critical because of the large number of tenants sharing storage. In vSphere 5.5, for VMDKs greater than 2TB in size, SEsparse becomes the default scheme for virtual disk snapshots.

Various enhancements were made to SEsparse technology in the vSphere 5.5 release, which makes SEsparse perform mostly on par or better than VMFSsparse formats. SEsparse also has a significant advantage over VMFSsparse virtual disk formats by being space efficient. We conducted a series of performance experiments, including a comprehensive set of Iometer workloads, real data-intensive applications like Hadoop MapReduce applications, and VDI workloads.

Overall, the performance of SEsparse is about 2x better than the VMFSsparse format for a random write workload and slightly better or on par with the VMFSsparse format for other workloads. One of the very few cases where VMFSsparse outperforms SEsparse is during sequential writes of very large block sizes like 512KB. The data generation part of the Hadoop TeraSort application issues large (512KB) sequential writes, so we have seen decreased performance in SEsparse for those cases. Improving the sequential write performance with large I/Os is being investigated.


For VDI environments, however, using the SEsparse virtual disk format increases the space efficiency of VDI desktops over time with no impact on user latencies. The space reclamation (wipe-shrink) operation in SEsparse has a 10% CPU overhead and should be scheduled during low server load. After the wipe-shrink operation completes, we observe slight improvements in user latency and CPU utilization. Overall, SEsparse is the recommended disk format for VDI workloads. 

Download this technical white paper: SEsparse in  VMware vSphere 5.5

Performance demands of latency-sensitive applications have long been thought to be incompatible with virtualization. Such applications as distributed in-memory data management, stock trading, and high- performance computing (HPC) demand very low latency or jitter, typically of the order of up to tens of microseconds.

Although virtualization brings the benefits of simplifying IT management and saving costs, the benefits come with an inherent overhead due to abstracting physical hardware and resources and sharing them. Virtualization overhead may incur increased processing time and its variability.

VMware vSphere ensures that this overhead induced by virtualization is minimized so that it is not noticeable for a wide range of applications including most business critical applications such as database systems, Web applications, and messaging systems.

vSphere also supports well applications with millisecond-level latency constraints such as VoIP streaming applications. However, certain applications that are extremely latency-sensitive would still be affected by the overhead due to strict latency requirements. In order to support virtual machines with strict latency requirements, vSphere 5.5 introduces a new per-VM feature called Latency Sensitivity.



Among other optimizations, this feature allows virtual machines to exclusively own physical cores, thus avoiding overhead related to CPU scheduling and contention. Combined with a pass- through functionality, which bypasses the network virtualization layer, applications can achieve near-native performance in both response time and jitter.

Briefly, this paper presents the following:

• It explains major sources of latency increase due to virtualization, which are divided into two categories: 1) contention created by sharing resources and 2) overhead due to the extra layers of processing for virtualization.
• It presents details of the latency-sensitivity feature that improves performance in terms of both response time and jitter by eliminating the major sources of extra latency added by using virtualization.
• It presents evaluation results demonstrating that the latency-sensitivity feature combined with pass-through mechanisms considerably reduces both median response time and jitter compared to the default configuration, achieving near-native performance.
• It discusses the side effects of using the latency-sensitivity feature and presents best practices.

Technical White Paper: Deploying Extremely Latency-Sensitive Applications in VMware vSphere 5.5

At the annual VMworld conference, VMware has introduced their vision for the software-defined datacenter (SDDC) in the future. The SDDC is the architecture for the cloud by VMware in which all pillars of the datacenter, including compute, storage, networks and associated services, are virtualized. In this white paper, they look at one aspect of the SDDC of VMware, the storage pillar. We specifically discuss how a new product called Virtual SAN (VSAN) fits into this vision.


VSAN is a new storage solution from VMware that is fully integrated with vSphere. It automatically aggregates server disks in a cluster to create shared storage that can be rapidly provisioned from VMware vCenter during VM creation. It is an object-based storage system and a platform for VM Storage Policies designed to simplify virtual machine storage placement decisions for vSphere administrators.

It is fully integrated with core vSphere features such as VMware vSphere High Availability (vSphere HA), VMware vSphere Distributed Resource Scheduler (vSphere DRS) and VMware vSphere vMotion. Its goal is to provide both high availability and scale-out storage functionality.

It can also be considered in the context of quality of service (QoS) because VM Storage Policies can be created that define the level of performance and availability required on a per–virtual machine basis. 

Download: What’s New in VMware Virtual SAN (VSAN)