For years, VMware promised to ease the pain of managing storage in its environment. Its new vSphere Virtual Volumes...
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(VVOLs) feature has a role in fulfilling this pledge.
VVOLs address many of the challenges associated with managing legacy storage systems in virtualized environments, but the key word is legacy. So, can modern storage systems like all-flash and hybrid storage arrays benefit from the implementation of vSphere Virtual Volumes?
To ease deployment, most environments create a few large LUNs and then place the majority of data stores associated with their virtual machines (VMs) onto that LUN. Putting multiple data stores on a single LUN makes it difficult -- if not impossible -- to guarantee a certain performance level to a given VM. The alternative is to create a LUN for every VM, but that becomes a management nightmare.
VSphere Virtual Volumes cross that chasm by creating a volume or LUN for each VM, and then managing those volumes transparently. This allows a storage administrator to manage the VM, not the underlying storage. Application performance can be fine-tuned because VVOLS provide more granular control. The technology is not perfect and, in some cases, may not be needed in the modern storage infrastructure.
The modern storage system almost certainly has some flash associated with it and most of these systems, especially hybrid systems, have features that ensure a certain level of performance to specific LUNs or volumes. But until recently, that performance guarantee was limited to a LUN-level granularity, not a VM level of granularity. The answer to whether vSphere Virtual Volumes is needed depends on the type of modern storage system deployed by the data center and the organization's expectation of using any legacy storage that may be available.
All-flash storage arrays and VVOLs
All-flash arrays may eliminate the need for VVOLs if the organization uses those arrays for all of its production VM data. This decision is a practical one, especially in a virtualized environment, thanks to deduplication and compression technologies.
These data efficiency technologies can deliver impressive results -- a 9:1 efficiency ratio is not uncommon -- in a virtualized infrastructure. And because these are all-flash storage systems with excess performance to spare, any performance overhead is virtually hidden from users.
The performance of all-flash systems also mitigates the need to adjust performance based on service levels. If the data center can afford to standardize on all-flash for the virtualized environment, there is a good chance it will provide more performance than needed. As a result, there is only one service level: really fast.
Where vSphere Virtual Volumes may be of interest is if the data center wants to augment the all-flash storage array purchase with a high-capacity disk array or even an object storage system. Using these arrays for less important or even dormant VMs can reduce the investment in the all-flash array system, especially over time. It makes more sense to expand a system that is priced at pennies per gigabyte (GB) instead of dollars per GB.
VVOLs enable the migration of data between all-flash array storage systems based on service level. A VMware administrator can decide to change the performance of a VM from Gold to Silver, and VVOLS will take care of the rest.
Hybrid flash storage arrays and VVOLs
A data center may also decide to purchase a hybrid flash storage array, which provides flash and hard disk drives, and automatically moves data between them.
Implementation drives how much one of these systems needs vSphere Virtual Volumes. For example, several hybrid systems already have a VM level of granularity built into them and can make determinations on where to place a VM data store automatically. An administrator armed with this level of granularity may decide to pin certain types of VMs to flash and exclude others.
Hybrid systems without a VM level of granularity are typically block-based devices with limitations similar to those of legacy storage systems. While they can place sub-components of a LUN in flash, this is done through the caching algorithm and cannot typically be overridden manually.
The only way around the lack of granularity is to create LUNs that are unique to the VM or a general performance profile. For example, a Gold LUN would be locked into flash and VMs that qualify for a gold level of performance would be assigned to that LUN. While not nearly as seamless as VVOLs, it would, at some level, accomplish the task of manually managing performance.
Most VMware environments have a mixture of storage systems; some are flash- or even all-flash-based, while others are hard disk-based. For these environments, VVOLs simplify how data moves between these tiers.
For environments that can consolidate into a single all-flash or hybrid storage system, vSphere Virtual Volumes may not be needed. All-flash eliminates performance-tuning by making everything fast. A hybrid system, especially one with VM-level granularity, can essentially provide its own cross-hypervisor VVOLs.
Storage arrays can benefit from vSphere Virtual Volumes
Use vSphere Virtual Volumes to gain on VM-centric and hyper-converged storage