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The Next Step in Thin Provisioning

Several months ago, in "A New Approach to Storage Provisioning", I wrote about a company called 3PAR ( and its thin-provisioning technology. In that article, I pointed out that the thin-provisioning model (which lets you provision for future storage needs by using physical storage that you haven't yet purchased) was a technology that would be greatly useful to storage administrators and well worth keeping an eye on.

Not surprisingly, other vendors--such as Zetta Systems ( including thin provisioning in their storage software. Thin-provisioning technology really hit the mainstream, though, when Network Appliance (, a leading Storage Area Network (SAN) and Network Attached Storage (NAS) vendor, incorporated thin-provisioning technology in the latest release of its Data ONTAP OS.

Data ONTAP ships with all of Network Appliance's filer systems (the vendor's name for its storage devices). Data ONTAP 7G adds, among other things, the thin-provisioning support. What's interesting about this latest version of Data ONTAP isn't only its thin-provisioning capability but also the introduction of what Network Appliance calls dynamic virtualization.

Dynamic virtualization combines two new technologies that Network Appliance includes in its software: FlexVol and FlexClone. FlexVol is the thin-provisioning piece; it supports the storage virtualization technology, which is a key factor in reducing the costs associated with provisioning and purchase of storage. Network Appliance believes that the most compelling advantage of FlexVol is its automation of virtual storage management. FlexVol enables multiple managed dynamic volumes to be distributed across large pools of disks. The storage virtualization that thin provisioning allows means that FlexVol should offer a simple and efficient storage-utilization methodology.

Network Appliance claims that its FlexClone technology lets you create data volumes and storage sets without requiring additional storage space when the replica is created. Most important for storage administrators, these replicas can actually be used for tasks such as testing, bug checks, OS upgrades, and data simulations without affecting the live data sets or requiring you to buy additional storage. With the FlexClone technology, Network Appliance takes the thin-provisioning concept a step beyond simply virtualizing potential storage needs and maximizing utilization of existing physical storage. FlexClone lets storage administrators build virtualized replicas of their storage environments and use the replicas to analyze current storage needs, perform goal-seeking analysis of potential storage or application changes, or simply test changes to the storage network before deploying them.

The key to these technologies' success is whether they actually fulfill the vendor's claims that dynamic virtualization can be accomplished with minimal effect on the performance of the existing storage networking infrastructure and no impact on specific devices when virtualized volumes are created. If Data ONTAP can provide these services without requiring you to buy more storage hardware or upgrading existing hardware, Network Appliance's technology will be immensely valuable to customers.

I tend to be a bit skeptical of announcements that seem to promise something for nothing (other than the cost of the software), but I'm occasionally proven wrong. I'd like to see Network Appliance's thin-provisioning and dynamic virtualization capabilities perform as the vendor says they will across its entire product line. Such improvements significantly help administrators justify the ROI arguments for storage networking.

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