Benefits of ESXi Host Local Flash storage

Count The Ways – Flash as Local Storage to an ESXi Host
Posted: 21 Jul 2014   By: Joel Grace

When performance trumps all other considerations, flash technology is a critical component to achieve the highest level of performance. By deploying Fusion ioMemory, a VM can achieve near-native performance results. This is known as pass-through (or direct) I/O.

The process of achieving direct I/O involves passing the PCIe device to the VM, where the guest OS sees the underlying hardware as its own physical device. The ioMemory device is then formatted with “file system” by the OS, rather than presented as a virtual machine file system (VMFS) datastore. This provides the lowest latency, highest IOPS and throughput. Multiple ioMemory devices can also be combined to scale to the demands of the application.

Another option is to use ioMemory as a local VMFS datatstore. This solution provides high VM performance, while maintaining its ability to utilize features like thin provisioning, snapshots, VM portability and storage vMotion. With this configuration, the ioMemory can be shared by VMs on the same ESXi host and specific virtual machine disks (VMDK) stored here for application acceleration.

Either of these options can be used for each of the following design examples.

Benefits of Direct I/O:

Raw hardware performance of flash within a VM with Direct I/OProvides the ability to use RAID across ioMemory cards to drive higher performance within the VMUse of any file system to manage the flash storage

Considerations of Direct I/O:

ESXi host may need to be rebooted and CPU VT flag enabledFusion-io VSL driver will need to be install in the guest VM to manage deviceOnce assigned to a VM the PCI device cannot be share with any other VMs

Benefits Local Datastore:

High performance of flash storage for VM VMDKsMaintain VMware functions like snapshots and storage vMotion

Considerations Local Datastore:

Not all VMDKs for a given VM have to reside on local flash use shared storage for OS and flash for application DATA VMDKsSQL/SIOS

Many enterprise applications reveal their own high availability (HA) features when deployed in bare metal environments. These elements can be used inside VMs to provide an additional layer of protection to an application, beyond that of VMware HA.

Two great SQL examples of this are Microsoft’s Database Availability Groups and SteelEye DataKeeper. Fusion-io customers leverage these technologies in bare metal environments to run all-flash databases without sacrificing high availability. The same is true for virtual environments.

By utilizing shared-nothing cluster aware application HA, VMs can still benefit from the flexibility provided by virtualization (hardware abstraction, mobility, etc.), but also take advantage of local flash storage resources for maximum performance.

Benefits:

Maximum application performanceMaximum application availabilityMaintains software defined datacenter

Operational Considerations:

100% virtualization is a main goal, but performance is critical.  Does virtualized application have additional HA features? SAN/NAS based datastore can be used for Storage vMotion if hosts needs to be taken offline for maintenance CITRIX

The Citrix XenDesktop and XenApp application suites also present interesting use cases for local flash in VMWare environments. Often times these applications are deployed in a stateless fashion via Citrix Provisioning Services, where several desktop clones or XenApp servers are booting from centralized read-only golden images. Citrix Provisioning Services stores all data changes during the users’ session in a user-defined write cache location.  When a user logs off or the XenApp server is rebooted, this data is flushed clean. The write cache location can be stored across the network on the PVS servers, or on local storage devices. By storing this data on a local Fusion-io datastore on the ESXi host, it drastically reduces access time to active user data making for a better Citrix user experience and higher VM density.

Benefits:

Maximum application performanceReduced network load between VM’s and Citrix PVS ServerAvoids slow performance when SAN under heavy IO pressureMore responsive applications for better user experience

Operational Considerations

Citrix Personal vDisks (persistent desktop data) should be directed to the PVS server storage for resiliency.PVS vDisk Images can also be stored on ioDrives in the PVS server further increasing performance while eliminating the dependence on SAN all together.ioDrive capacity determined by Citrix write cache sizing best practices, typically a 5GB .vmdk per XenDekstop instance.

70 desktops x 5GB write cache = 350GB total cache size (365GB ioDrive could be used in this case).

The Citrix XenDesktop and XenApp application suites also present interesting use cases for local flash in VMWare environments. Often times these applications are deployed in a stateless fashion via Citrix Provisioning Services, where several desktop clones or XenApp servers are booting from centralized read-only golden images. Citrix Provisioning Services stores all data changes during the users’ session in a user-defined write cache location.  When a user logs off or the XenApp server is rebooted, this data is flushed clean. The write cache location can be stored across the network on the PVS servers, or on local storage devices. By storing this data on a local Fusion-io datastore on the ESXi host, it drastically reduces access time to active user data making for a better Citrix user experience and higher VM density.

VMware users can boost their system to achieve maximum performance and acceleration using flash memory. Flash memory will maintain maximum application availability during heavy I/O pressure, and makes your applications more responsive, providing a better user experience. Flash can also reduce network load between VMs and Citrix PVS Server.Click here to learn more about how flash can boost performance in your VMware system.

Joel Grace Sales Engineer
Source: http://www.fusionio.com/blog/count-the-ways.

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