Looking at enterprise storage is a daunting task. For years we have looked at the cost per gigabyte, cost per performance, and other metrics. We have differentiated solutions based on small differences and what value they provide. In Healthcare, we are particularly focused on solutions that are “certified” for our applications, with many enterprise healthcare environments running a number of storage platforms.
A case for policy driven storage
Early in my career I became involved in Storage Engineering. I understood how the storage system worked, and I was able to quickly provision, and document what I was working on. It was tedious, and there weren’t many people on the team who had the confidence to work on the system. Storage tiering was either a manual process, or sometimes functions of add on software. Deduplication and compression were all post process, and SSD was prohibitively expensive. As we progressed, the technology didn’t really change much until the “All Flash Array” (AFA) was introduced. Inline deduplication and compression were born out of necessity, and we saw the cost of SSD technology drop to the point where we expect to see Fibre Channel/SAS drives become irrelevant in the coming years.
This change has brought out a need to do things differently. We have seen many vendors release better products; bigger, faster, with more features. But the way we have handled storage at the virtual layer hasn’t kept up with improvement. While capabilities like the VAAI have improved with each release, and we have continued to offload more and more of the storage workloads to the storage array, the way we manage the storage has not changed. We have continued to present storage in a big logical drive and then proceed to share it among a number of virtual systems. Not a terrible way to go, but that leaves performance and features on the table. There must be a better way.
What does Policy Driven Storage look like?
To take full advantage of the new capabilities, we needed to find a way to remove some of the layers of abstraction. As with anything, generally speaking, the fewer layers between two components the better. In order to manage directly though, we need a common interface, a common way of doing things. Again with the multiple storage vendors we often find in many healthcare environments, it is important to manage each through a common set of policies. Things like performance, deduplication, compression, or anything a system is capable of providing, should be handled at the individual virtual disk level. This also makes replication and recovery far more granular and manageable.
To make policy driven storage a reality, VMware gives two different options. Virtual Volumes (VVOLs), and Virtual SAN (VSAN). These are two different ways of getting to the same point, and both have their merits. The real value is that policies can be used to manage both, and once configured, it becomes seamless to the VMware administrator.
The concept behind VVOLs is not so much different from the original VASA. We have worked with our storage partners and they have exposed their capabilities to a common interface. Previously vendors would install plugins to manage their storage through vCenter, with some tasks offloaded to the storage array. The interfaces varied in their value, and didn’t really provide a unified way of managing the storage; especially for a customer having multiple array vendors.
With the introduction of VVOLs, a policy is created to enable a variety of attributes, such as high performance and deduplication. When a VM is created or moved, the VMware administrator is provided a list of compatible datastores to select from, based on the policy. If the workload changes, the administrator may change policies and move the workload to a more appropriate datastore. This is available because the storage array advertises its capabilities to the virtual environment. The storage policies are then created based on these advertised capabilities. Since everything is handled by the array, there is lower overhead on the host, and more granular control since each VVOL is a separate object rather than a group of objects on a single lun.
VSAN is the next generation of Software Defined Storage (SDS). The general concept behind software-defined storage is taking disks internal to a host server, and using them to create a logical storage system. This is managed through software, and historically has been done as a virtual machine controller sitting on each host.
VSAN differs because it is a kernel module, built into the hypervisor itself. This removes much of the complexity, and overhead typically associated with SDS. The deployment and expansion is literally only a few clicks, and provisioning storage is as simple as creating a policy.
Because VSAN is designed to be policy driven, it becomes incredibly simple to manage, and we often find that it is considered to be a part of the VMware system by customers who deploy it. Since it is server-based storage, the storage team does not often need to be involved.
It is important to note, the concept of a datastore changes with both VVOLs and VSAN. Each virtual disk becomes a lun on the storage array, or in the case of VSAN, a series of separate objects. The policy simply manages the placement of the objects, and what capabilities it needs. The Datastore simply appears as a higher-level construct representing a logical grouping of similar virtual disks, not a logical device as previously.
The Healthcare Difference
What is the value of policy driven storage for healthcare? Aside from the simplified management, ease of deployment and granular control, policy driven storage unifies the various types of storage. In many of our customers we find that multiple vendors provide storage arrays with varying capabilities. This often requires working with different members of the storage team to provision new storage capabilities, and creates challenges when upgrades are required or new implementations.
As we look at healthcare we regularly encounter with new regulations, new requirements, and we always seem to be struggling to keep up with the latest trends. By using a policy driven approach, we can not only respond more quickly to our customers and security teams, but we can also create cross functional teams who can provide more value to the internal customer, and ultimately to our end customer, the healthcare