by Bob Fine, Director of Product Marketing — July 28, 2008

On our last post we were discussing specific features of Compellent’s thin provisioning solution, Dynamic Capacity. And today we’re continuing that conversation to discuss potential green benefits, recovery and reporting.

Does thin provisioning result in any green benefits?
Thin provisioning is a must-have technology for a cost-effective, green data center. By purchasing and operating fewer disk drives, companies can significantly reduce power, cooling and physical space costs. Using thin provisioning alone, without any other energy-saving features, can help companies reduce disk drive counts on just a single tier of storage by 75 percent. Analysts estimate the storage utilization rates for traditional SANs are as low as 25 percent.

For example, a typical storage system—without thin provisioning—might require 274 146-GB disk drives to provide 10 TB of storage capacity (assuming 25 percent storage utilization). By contrast, a Compellent SAN using thin provisioning with the same type of drives would require only 69 146-GB disk drives to provide the same usable storage capacity. Eliminating 105 disk drives from the data center can mean a significant reduction in energy consumption and carbon emissions in addition to the smaller footprint.

What about data migration and recovery processes?
Thin provisioning solutions can also improve efficiency and utilization when end-users transfer data from their legacy storage systems. For example, Compellent’s Thin Import feature in Storage Center 4.0 converts data from a “thick” provisioned volume to a thin-provisioned volume during the migration process. Unused space from the legacy volume is freed up to be allocated to another volume in the Compellent SAN.

In Windows environments, deleted files aren’t really returned to the storage pool even in thin-provisioned volumes. Often, users turn to a third-party utility to defrag the Windows volume to free up the unused space. Without these utilities even a thin-provisioned volume becomes thick. Compellent integrates a utility to recover this unused space called Free Space Recovery in Enterprise Manager, our SRM tool that automates replication, storage and green cost savings reports and chargeback, keeping volumes as thin as possible.

How extensive are management and reporting tools?
The Compellent SAN monitors capacity utilization in real time and provides information to administrators so they know exactly what the disk space consumption is at all times. The SAN sends alerts (like e-mail and text messages) based on pre-defined rules.

Enterprise Manager also shows storage utilization and consumption over a period of time including allocated space, used space and configured space for all disks and total space and used space for any RAID selection with any disk tier. Admins can also view ongoing CPU and memory utilization for each SAN to understand how utilization is affecting performance. They can generate “hero” reports to document storage ROI for senior management, charge back departments for storage utilization, and show savings on energy and carbon emissions.

As energy costs continue to skyrocket, we expect more customers to take advantage of thin provisioning technology as they start to realize the lowered disks and power and cooling costs associated with thin provisioning. Especially as organizations look to migrate data off of aging DAS and legacy SAN storage systems to more flexible next-generation storage arrays.

After reading this, are there still areas of thin provisioning that aren’t clear for you? Leave me a question, I’m happy to answer it.

by Bob Fine, Director of Product Marketing — July 25, 2008

Not all thin provisioning products are created equally—some are thinner than others. Industry experts like Rich Friedman at Storage magazine and Mario Apicella at Infoworld, recently posed interesting questions about different features, cost reductions and energy savings of thin provisioning solutions. Given this, we thought it would be helpful to explain Compellent’s approach and what makes our thin provisioning software, Dynamic Capacity, unique.

Diving into the virtual storage pool
Compellent manages data inside the volume, at a granular, block level. Dynamic Capacity works with our storage virtualization technology to make all physical disk space available to all volumes from a single shared storage pool. First, we spread read/write operations across all of the disk drives, rather than limiting availability to a single drive or group of drives dedicated to a volume. This means there aren’t the typical restrictions of RAID grouping or space pre-allocation. Users can create volumes of any size and number, and those volumes can simultaneously utilize all of the disk drives in the shared storage pool, resulting in better performance.

How does thin provisioning work?
Dynamic Capacity allows the creation of volumes without having to pre-allocate disk space. In other words, Compellent only allocates volume space when actually writing to disk. For example, if a server application requires 1 TB of storage, a customer can provision the space the application needs, even though there might be 500 GB of physical capacity.

So no more “islands” of storage?
Competitive thin provisioning solutions actually require end-users to pre-allocate physical capacity to create thin-provisioned volumes. Once the space is used up, the volume can’t be expanded. When unused it becomes an “island” of storage and can’t be returned to the storage pool, resulting in wasted storage space. Due to this, some vendors don’t enable or recommend their thin provisioning solution 100 percent of the time. To take advantage of the full benefits of thin provisioning, make sure the thin provisioning technology you are considering will always remove these “islands,” allow you to expand the volume on the fly and return any unused space to the storage pool.

What is the maximum pool size?
Compellent’s Dynamic Capacity has unlimited pool size.

What is the typical oversubscription ratio?
Ratios of real to oversubscribed capacity vary. Some users tell us they oversubscribe by 50 percent while others use a 2-to-1 ratio.

Another way to look at this is capacity planning – it’s not unheard of for thin provisioning users to plan 6-12 months in advance for drive purchases. They still allocate the volumes based on projected needs but they’d purchase fewer drives – often 50 percent fewer.

What about performance?
With thin provisioning, there’s less data being written to the disk, so common operations such as copy, replication and RAID rebuilds require disk access perform faster because they are based on actual data written within a volume instead of based on an artificially large allocated volume. The smaller the amount of data you have to write or re-write, the faster the performance. Some thin provisioning solutions, like Compellent’s, also match the chunk or page size of the data being written with your server application to optimize performance.

Consequently, Compellent thin-provisioned volumes can be expanded while the system is online without any downtime. Through automated tiered storage, the Compellent SAN can also dynamically move data to less-used disks if system bottlenecks occur. Compellent takes this a step further with Fast Track, because frequently accessed blocks are placed on the outer edges of drives to improve performance by as much as 30 percent.

What is the chunk or page size?
Compellent users can scale the chunk or page size from 512KB to 4MB depending on the server application. Smaller page sizes, like 512KB, improve performance for databases while larger 4MB page sizes improve performance for large I/O such as image processing.

To be continued…
In the next post we will look at green benefits of thin provisioning along with recovery process and reporting functions, so please stay tuned.