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New Dell SC Series operating system adds dedupe, QoS

Dell launches an operating system update for its SC Series storage arrays, featuring dedupe, QoS, Live Migrate, VVOLs support and new management capabilities.

The pending acquisition of EMC hasn't slowed Dell from bolstering its SC Series storage array with major new enhancements.

Dell today unveiled the Storage Center Operating System (SCOS) 7 for its SC Series (formerly Compellent) midrange array line, featuring block-level deduplication and enhanced compression. The company claims the new data reduction can lower the price of Dell SC flash tiers, using triple-level cell NAND, to 45 cents per gigabyte and hard-drive tiers to 10 cents per gigabyte based on a data reduction ratio of 4:1.

Travis Vigil, executive director of product management for Dell Storage, said the average capacity reduction is between 3:1 and 4:1, and the capacity savings have reached 10:1 with some workloads.

Other new capabilities in SCOS 7 include:

  • Quality of service (QoS) to prevent noisy neighbor problems and set performance for the most important workloads;
  • Live Migrate to enable administrators to move volumes between SC Series arrays without disruption to applications or impact to server-side mappings; and
  • Support for VMware VVOLs to enable provisioning, monitoring and management at a virtual machine (VM) level.

New Dell Storage Manager software shifts from Java to an HTML5-based interface that customers can use with the SC, PS and FS product lines. SCOS 7 enables customers to replicate bidirectionally between the Dell SC and PS Series (formerly EqualLogic) arrays and manage the systems through a single user interface. The Web interface is available now for the SC Series and will be ready later for the PS Series.

Alan Atkinson, vice president and general manager for Dell Storage, said the SCOS 7 is "the biggest feature release we've ever done." The last SCOS release was version 6.7.x, which became available to key customers last September and to all customers in February.

The SC Series is Dell's flagship primary storage array, but Atkinson said Dell would also continue to support and develop the PS Series, with a major release planned for this year. The last major PS update was version 8.0 in June 2015, coinciding with the release of the PS6610 model.

"There is no plan to end-of-life the PS," Atkinson said.

Laura DuBois, group vice president for IDC's enterprise storage, server and system infrastructure software research, said the most compelling features with the new Dell SC operating system release are the ability to manage dissimilar SC and PS systems. That is done through Dell Storage Manager and the PS-to-SC replication.

"With other vendors, you have to buy management for system one and management for system two," DuBois wrote in an email. "And if you want to replicate between systems, you have to buy a replication appliance. I think this work speaks to the commitment to help PS customers versus just [selling] them something new."

Dell SC Series data reduction draws praise

SherWeb, a cloud provider based in Sherbrooke, Que., is phasing out its PS Series arrays and currently has more than 24 Dell SC systems spanning five different models. But Samuel Nadeau, SherWeb's IT director for infrastructure and cloud services, doesn't foresee a need for Dell's new bidirectional replication capabilities, because VMware-certified staffers use VMware replication for the migration.

For Nadeau, the big new features in SCOS 7 are dedupe and compression. Dell first made available compression two years ago with SCOS 6.5, and enhanced it in subsequent 6.6 and 6.7 releases. But Nadeau said SherWeb could not use the compression on active data with a single tier of flash with its 6.6 code base.

"Compression was available only for inaccessible pages, and since we do not have very long retention of snapshots, it was not beneficial for us," he said. "With the version 7 release, we can now compress active pages."

SherWeb, an SCOS 7 beta tester, achieved a data reduction ratio of 3.7:1 with a mix of application workloads, including ERP systems and Microsoft's SQL Server, SharePoint and Exchange, according to Nadeau. He said he has seen no effect on write performance and only a bit of added latency on reads with all-flash configurations -- "not enough that our customers would notice."

Many all-flash array vendors offer inline deduplication and compression that performs data reduction before writing the data. SC arrays will dedupe the data after writing it, but Vigil claimed Dell provides "the same basic effects of inline deduplication" with its near-line approach.

"The way that deduplication works is basically all of our writes come in at RAID 10 onto flash media, so that's very high-performance writes. Then, when you take a snap of that data or you progress that data to a different tier, that's when deduplication occurs," Vigil said.

"If you look at the way people do deduplication, it requires some holding space for work to be done on that data. And in some competitive products, that holding space is a big chunk of RAM. On our product, that holding space happens to be the [solid-state drive] tier in our architecture," Vigil said. "You're writing into a landing space at very high performance -- RAID 10 performance -- and that makes it so that there's no performance impact on writes. So, we like to refer to it as near-line."

Vigil said deduplication requires compression to be enabled, but customers can choose to run compression by itself. Compression occurs on the lowest tier of the SC array, and if there's only one tier, it occurs on that tier to minimize the performance effect, Vigil said.

Nadeau said he's "not that picky" about whether data reduction is inline or post-process.

"Data reduction is data reduction for us," Nadeau said. "I'd much rather have better performance during the day, and it's going to process the data reduction at night. And I still have the option [with the Dell SC Series] to enable it or disable it. Most of the vendors that have inline dedupe do not have the ability to turn it off.

"That's a bit of an issue with VMs that are encrypted. There's really no point in trying to dedupe and compress this information. I'd much rather have the ability to turn [data reduction] off when I know it's not needed or there's not any benefit in using it."

Nadeau said he also expects SherWeb would use the new QoS capabilities with the Dell SC arrays, although he said the company also has QoS capabilities through its hypervisors. He said the application would dictate whether they use VMware's per-VM granular QoS or Dell's new QoS. He said some customers have applications requiring physical servers, and for those workloads, SherWeb would use Dell's QoS.

Henry Baltazar, research director for the storage channel at 451 Research, wrote in an email that Dell's new QoS feature is good, but "not as refined as competitors, such as SolidFire, which have been doing this for years and have abilities such as burst mode to better utilize storage performance."

Baltazar said after Dell's acquisition of EMC is complete, he expects to see EMC's storage assets positioned for the high end of the midrange and the core enterprise market. He predicted SC would "continue to be strong in the lower end of the market, where EMC had not been as successful."

SCOS 7 is a free upgrade to customers with support contracts. PS Series customers with a support contract can upgrade at no charge to new PS 9.0 firmware to get the unified management and replication capabilities. Replication is a separate license for the SC Series, starting at around $7,000.

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