Flash storage: Guide to enterprise all-flash storage arrays
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IBM recently joined the growing list of vendors claiming to surpass a million IOPS with its announcement that its new FlashSystem 840 doubled the performance and bandwidth of its predecessor, the FlashSystem 820, and dropped the read and write latency down to barely detectable microseconds.
How well IBM's purported 1.1 million IOPS stacks up against the millions of IOPS boasted by seven other all-flash array vendors will remain a mystery unless all vendors agree to use standard testing methodology. Until that day, suffice it to say, they're all faster than disk-based arrays.
We do know the FlashSystem 840 appliance lacks many of the storage-saving and management features increasingly showing up in performance-focused enterprise all-flash arrays. That's where IBM passes the baton to its FlashSystem V840 Enterprise Performance Solution, which bundles the FlashSystem 840 and IBM System Storage SAN Volume Controller, or SVC, software stack.
The FlashSystem V840 array supports such capabilities as thin provisioning, inline compression, snapshots, replication, data encryption and quality of service, whereas the 840 checks off only encryption and QoS from that list. Neither product supports inline deduplication.
"The reason we have two products is there's a segment of the market that needs extreme performance. They are truly doing application acceleration. And they don't want any bells and whistles getting in the way," said Kevin Powell, business line program manager for IBM FlashSystem.
Powell said the other half of the market uses flash as an alternative to hard-disk drives (HDDs). Those organizations want high performance and low latency but also need the enterprise features they're accustomed to using with their traditional disk-based storage systems.
Customers do have the option to completely configure IBM's disk-based systems, such as the DS8000 and Storwize arrays, with solid-state drives. But Powell said IBM doesn't count those products in the same camp as the arrays designed to take advantage of flash technology.
IBM got a running start in the purpose-built flash array market with its 2012 acquisition of Texas Memory Systems (TMS). By April, IBM was putting out its own branded versions of TMS products -- the FlashSystem 710, 720, 810 and 820 -- with such minor updates as an improved graphical user interface. This year's FlashSystem 840 and V840 mark "the first real IBM products," according to Powell.
"We built the flash modules, the controllers, the interface cards, everything, so that we minimize the latency," he said. "It's not just flash running through a disk system."
Few all-flash arrays use flash modules custom-built by the vendor. IBM sources its NAND flash directly from the manufacturers, and its proprietary enterprise multilevel cell (eMLC) modules are lengthier and about 50% wider than a standard 2.5-inch disk, according to Powell. They also buck the industry trend toward cheaper MLC flash.
"We purposely chose eMLC technology over lesser-grade MLC because the IBM customer set is more of an enterprise customer set," Powell said. "We are focused on reliability."
Powell said IBM has worked on write protection, wear leveling and other features to improve the endurance of its flash modules. He noted that IBM designed the system targeting "five-plus years of endurance" for a typical to heavy workload, although extreme use cases could potentially wear out the flash more quickly.
"All flash technology, from all vendors, will wear out over time based on the number of erase cycles," Powell said, adding that IBM does not state or publish a guaranteed number of reads or writes.
IBM places caveats on its flash warranty. The overwhelming majority of all-flash-array vendors say they would replace flash drives even if they wear out before the product warranty expires. Powell said IBM replaces failed products due to bad components or other malfunctions, but flash read/write wear-out is not covered under the warranty.
"Our service and support organization is here, and we can construct a contract as necessary for any customer requirements we need to," Powell said. "IBM has a long history of supporting customers for very long durations with our mainframe and our enterprise storage systems, so we know how to take care of enterprise customers."
IBM continues to sell and support FlashSystem 710, 720, 810 and 820. But Powell said those products will "phase out before the end of this year."
List prices begin at $50,000 for the FlashSystem 840 and $100,000 for the V840. IBM claims a price per gigabyte (without compression) of $14.08 for the 840 and $14.70 for the V840, and a per-IOPS price of 33 cents for the 840 and 60 cents for the V840.
IBM said there is 50% performance degradation during controller failure. Data is accessible during controller failure.