Rethinking Storage for Virtualized Infrastructures

Traditional storage systems mainly use LUNs and File Systems (FS) as provisioning and management units; LUNs for the block-wise access, FS for the file-level, and both when it comes to unified storage. For iSCSI, FC, and NFS (CIFS), the level of granularity is LUNs and files. What is wrong with the storage granularity? Why are LUNs and files not enough now?

A big reason is that infrastructure has become increasingly virtualized. Today, virtual server is a default deployment option for many enterprise deployment policies.

Clearly, infrastructure virtualization is not a secret (nor is storage virtualization). The point is that traditional storage arrays that are very effective working with physical servers become less so when the servers are virtualized.

In single host I/O patterns, storage arrays are smart enough to understand when a LUN is dedicated to a single host or when it is shared and there is a possibility to track the hosts with some identifier (i.e. World Wide Name). Additionally, caching techniques that help improve the array’s external performance can be effectively used, in this case to pre-fetch the data from the internal drives.

However, these performance improvements fall short when it comes to virtualized hosts, due to the fact that I/O from the different VMs is coming the same way and storage is unaware of this. Data protection/copying/movement features are also impacted since the same LUNs are used by numerous virtualized hosts. LUN level locking is a significant issue in such cases. It is here that the emerging concept of VM granular storage comes into play. This is a rethinking of the storage arrays which takes into account the virtualized infrastructure reality and elevates the importance of VMs in storage systems. VMware Virtual Volumes (vVols) is a solution of this type.

In this Knowledge Sharing article, Alexey Polkovnikov delves into the concepts, history, and context of VMware vVols technology. His article will be of particular interest to those involved in storage infrastructure planning, decision-making, and implementation.

Read the full article.