Traditional volumes have been around as long as we have had file systems, but now may be the time to pronounce the end of the storage volume. As data centers get larger and storage systems are populated with more and more physical drives they are growing into a storage manager's nightmare. There are just too many volumes of drives to be managed effectively.Volumes were simple at first, there was a 1:1 relationship between servers and physical disk. However, there was a need to increase the level of protection; we started to add a second drive for mirroring or multiple drives for RAID. Now there was a 1 to many relationship between servers and drives. Next came the SAN and with it Logical Unit Numbers (LUNs). Then we had multiple servers each connecting to a volume and each of these volumes shared a LUN. Finally came server virtualization and now the storage manager has to deal with many virtual machines hosted by a cluster of physical hosts all with shared access to volumes that in turn may shared specific LUNs. Its enough to make you want to consider another career or at least become an application guy.
Companies like 3PAR, Compellent and ZFS based products like Nexenta are trying to break the volume based model to a pooled storage approach. All the storage is placed into a globally available storage pool. All the servers have access to all of the storage, you just need to tell each server how much capacity it can have and possibly what tier of storage it can use. There are no LUNs and specific volume assignments to manage.
The key gain here is the elimination of the time spent by storage managers managing LUNs and volumes. A shared storage pool essentially reduces the job to one of managing global capacity and as we discuss in our article on Thin Provisioning Basics, most pooled storage systems provision capacity thinly. In actuality you are only managing used capacity.
The storage system will make decisions on what data should go where automatically. Some of these systems can self-optimize themselves to deliver better performance by moving data to the edge of hard drive platters, wide striping data or by automatically migrating between tiers of storage.
For some storage managers, losing the feeling of control of knowing exactly what data is on which drives is the biggest challenge. While most pooled storage systems will let you provision storage in the classic hard set, this data goes here method it is not ideal. Given the stack of virtual machines, physical hosts, SAN, Volumes and LUNs, the data center now deals with the classic model has become almost unmanageable. Letting the storage system do the work is a better use of the storage manager's time.
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George Crump is founder of Storage Switzerland, an analyst firm focused on the virtualization and storage marketplaces. It provides strategic consulting and analysis to storage users, suppliers, and integrators. An industry veteran of more than 25 years, Crump has held engineering and sales positions at various IT industry manufacturers and integrators. Prior to Storage Switzerland, he was CTO at one of the nation's largest integrators.