Article Written by Judy Kaldenberg, Product and Solutions Marketing Manager, Nexsan  

Storage operations have become a growing area of focus for performance improvements, since there are so many advantages that come from virtualizing IT resources using VMware. The goal for storage administrators and IT management should be to elevate storage management up to the same level of efficiency, automation, and performance as other VMware operations. By optimizing storage management, organizations can see a number of immediate benefits including:

• Greater flexibility and efficiency of IT
• Improved usage of server and storage resources
• Administrators free up time spent maintaining VMware
• A more agile business
  

Speedier Storage Area Networks

In a vSphere environment, the principal resource management issue for storage relates to data movement and speed. Traditionally, common administrative operations required reliance on software-based data movement that was relatively slow and caused drags in performance.

Part of the sluggishness results from having VMkernel Data Mover issue input/output (I/O) commands to read and write blocks in the source and target datastores. This process consumes excessive system resources on the vSphere server, including central processing unit cycles on host servers and Small Computer System Interface (SCSI) commands in the host bust adapter queue.

Using vSphere Storage APIs for Array Integration (VAAI) with a block storage system, vSphere can easily issue a command to the array, which completes it while avoiding performance bottlenecks at the host level. The jobs of cloning, migrating virtual machines, and creating zero blocks-which are all I/O-hungry work-can now be accelerated by hardware within the array itself. The result is that many storage operations will experience drastically improved performance.

Behind the Performance Improvements

Three application performance interfaces-or "primitives"-comprise VAAI: Atomic Test and Set (ATS), Hardware Accelerated Copy (HAC), and Block Zero. The right storage management system can activate these primitives by default. Here is how each works:

• ATS improves performance and manageability when performing operations on virtual machines (VMs) that require locking. Before ATS, when an administrator needed to make a state change to a VM, VMware ESXi would lock the whole storage pool-including the resident VMs- prior to the operation using a SCSI reservation. But locking granularity is greatly improved using ATS. This is because the vSphere host now locks only those specific blocks on which the VMs being cloned or moved reside. This allows access to other VMs on the logical unit number (LUN) by multiple hosts. Administrators can use the benefits of ATS to increase their consolidation ratio, secure in the knowledge that even during administrative operations, they can keep multiple VMs available to multiple hosts.
  

• When it comes to common storage-intensive tasks like cloning and migration of VMs, HAC offers dramatic performance improvements. Without HAC, cloning and migration required intensive I/O through the vSphere host server utilizing extensive bandwidth. This would often challenge the host's resources, delaying the performance of other tasks. By using HAC, the vSphere host can offload these I/O operations and leverage the native array EXTENDED COPY SCSI-or XCOPY-command. The vSphere host issues a copy or migrate command through vMotion, and the operation is completed between the source and target LUNs or arrays. The result is that CPU, memory, fabric, and other host resources are freed up, boosting performance.
  

• Block Zero offers similar efficiencies for creating new virtual machine disks. It used to be a very time-consuming and resource-intensive process to write zero blocks for fault-tolerant VMs. That's because every single command for zeroing a block had to move from the vSphere host, to the array, and back to the host for acknowledgement. Block Zero ensures that optimized commands in the array replace these redundant host-based I/O write commands. Once the host issues a command, the array can finish the WRITE SAME SCSI operations within the storage infrastructure, freeing up the vSphere host's resources for other jobs and cutting the time needed for zeroing operations.
  

Additional Management Capabilities

Using a solution to optimize storage management also allows administrators to integrate a key feature of VAAI that delivers additional management capabilities for block storage. This "thin provision" feature can facilitate higher availability for VMs while improving storage management for a thin-provisioned environment. Without this feature, administrators needed to use a manual process to determine when a thin-provisioned volume was reaching maximum capacity. When the volume reached its limit, VMs could crash, corrupting data and causing negative impacts to the business. Another problem with the old system was that once an administrator freed up capacity by migrating or deleting a VM, the vSphere host lacked any mechanism to notify the array that the blocks were now free.

With a thin provision feature, the administrator can set a capacity for thin-provisioned volumes. Once capacity exceeds that limit, the array sends out a notification to vCenter. This allows the administrator maximum flexibility to manage the array proactively-for example by adding capacity, issuing a vMotion command, or extending the datastore. The result is that critical VMs continue operating without challenges on storage capacity.

In short, finding the right solution for storage management is the key to unlocking virtualization performance. The right solution can not only boost storage management to the efficiency and performance levels of other VMware operations, but it can also add benefit throughout the organization by improving IT flexibility, efficiency, resource utilization, and ultimately business agility.

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About the Author

Judy Kaldenberg, Product and Solutions Marketing Manager for Nexsan, joined the company in March 2015 and is responsible for product marketing, solutions marketing, sales enablement and partner alliances. She has more than 25 years of experience working with IT infrastructure and applications in many capacities including technology sales, marketing, channel management, and application development. Judy holds a Bachelor's Degree from Truman State University.