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In virtual server environments, storage is often the single biggest factor in determining overall performance. But what is the best type of storage for server virtualization? Believe it or not, there is no simple answer to this question.
There are a number of hypervisors on the market, each with its unique storage requirements. Every available storage type has its own strengths and weaknesses: some are better able to deal with extreme IOPS requirements, while others might have a low cost per gigabyte of storage. Hence, there is no such thing as a perfect method of storage for server virtualization. This article discusses three storage options that work particularly well with virtual servers.
Option 1: Hyper-converged
Over the last year, there have been a number of storage vendors and industry analysts who have proclaimed that hyper-converged infrastructure will soon be the standard for server virtualization. Although such a strong statement is certainly up for debate, there is a very good reason why hyper-converged infrastructure is becoming so popular.
Hyper-converged storage systems are specifically designed for use with virtual servers. All the major components (CPU, storage, network and so on) are certified to work with one another and to be compatible with the hypervisor vendor's software. This is the advantage to using hyper-converged storage for server virtualization: the storage is included with the rest of the hardware, usually preconfigured and guaranteed to provide an optimal experience.
Unfortunately, the downside to using a hyper-converged infrastructure is that storage is an integrated component. If you need to increase storage capacity, you may have to purchase additional modules, even if you don't need the compute or network resources that are included with those modules. The cost to increase storage capacity would likely be higher than if you used a different type of storage.
Option 2: Storage virtualization
Storage virtualization is a somewhat generic technology because it can be implemented in a number of ways. The Windows Server operating system, for instance, can provide storage virtualization through its Windows Storage Spaces feature.
The basic concept behind storage virtualization is that the physical storage is masked by an abstraction layer. This abstraction layer allows multiple, physical storage devices to be aggregated into a single, logical storage device.
But storage virtualization is about more than mere capacity aggregation. If that were the only goal, it might be easier to simply build a RAID array.
As previously mentioned, each vendor has its own way of virtualizing storage. In some cases, storage virtualization may combine multiple NAS appliances into a single, logical storage device. In other situations, storage virtualization might be used to create a logical storage device out of various disks.
One thing that tends to set storage virtualization apart from a normal storage array is that storage virtualization often allows the capabilities from different types of storage devices to be combined. Suppose storage virtualization was used to create a logical disk made up of both solid-state drive (SSD) and hard disk drive (HDD) storage. In this type of situation, the abstraction layer would likely use the SSD storage as a high-speed tier that acts as a read/write cache and the HDDs to store less frequently accessed data. This approach works very well for server virtualization because the high-speed tier could help to absorb spikes in IOPS, while the standard tier (made up of HDD storage) would likely have sufficient capacity to store the various virtual hard disks.
Option 3: Cloud storage
Cloud storage also tends to work well for virtual servers. However, current bandwidth limitations tend to make it impractical to migrate all your virtual hard disks to cloud storage while the virtual machines (VMs) continue to run on premises. Even so, cloud storage does have its place.
Not all that long ago, cloud vendors were engaged in an all-out marketing push to get customers to move all their resources to the cloud. Today, most have accepted the idea that some VMs are better suited for use in the local data center, while others work better in the cloud. As such, the cloud is often treated as an extension to the local datacenter. Services such as Microsoft Azure and Amazon AWS allow administrators to not only run VMs in the cloud, but to set up cloud storage that can be utilized for a variety of purposes.
Even though cloud storage probably isn't a good fit for general-purpose storage, it does have its uses. For example, an organization that needs to temporarily scale-up a workload might create cloud VMs to complement what is already running locally. Similarly, some organizations move data archives to cloud storage to free up local storage capacity.
Ultimately, there is no such thing as a VM storage type that is well suited to every conceivable use. Thankfully, modern hypervisors can use a variety of storage types, which allows administrators to choose the type of storage for server virtualization that best meets their needs.
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