Flash storage: Guide to enterprise all-flash storage arrays
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Hitachi Data Systems Corp. (HDS) may not sell an array that was designed at the outset exclusively for flash, but the company has expended considerable effort to optimize its Hitachi Unified Storage (HUS) VM for the ultra-fast storage media.
HDS took the unusual step of building its own flash module drives (FMDs) and made flash-specific modifications to its Basic Operating System (BOS) to help the HUS VM crack the million read IOPS threshold that growing numbers of all-flash array vendors claim.
The HUS VM is among a handful of all-flash arrays to use custom-built flash drives. Hitachi's FMDs can store 3.2 TB and boost the array's maximum flash storage capacity to 302 TB, making it one of the higher capacity all-flash arrays on the market.
We can ship a 600 TB flash system today with VSP with no issue, but the use cases for 600 TB of flash in one system are relatively small.
FMD includes multilevel cell (MLC) NAND media, battery backup and a custom-designed embedded controller. The company claims that it has either received or applied for more than 60 patents for drive technologies such as custom error-correcting code (ECC) to monitor page degradation and avoid premature page rewrites.
With its initial release in September 2012, the first all-SSD-capable HUS VM achieved about 250,000 read IOPS. A June 2013 release boosted performance for a single system to about 500,000 read IOPS, and an October update doubled the number to 1 million, according to Bob Madaio, senior director of infrastructure platforms marketing at HDS.
Madaio said the performance bump to 500,000 IOPS stemmed from a system software upgrade branded as Hitachi Accelerated Flash (HAF), and the leap to 1 million IOPS resulted from further flash optimizations for which the HDS adds a "small upcharge" relative to the overall system cost. HDS field representatives can advise customers if they will be able to achieve 1 million IOPS based on how their applications work.
"We all market these high IOPS numbers, but what really matters is low and consistent response time," he said. "A million IOPS performance takes a very special high-intensity read environment to really make sense."
Madaio said some users may need performance at all costs, but most scenarios don't require a million IOPS. Likening all-flash arrays to rocket ships and disk-based arrays to cars, he said, "Yes, there are different models of rocket ships, and I guess one is faster than the other. But, everyone was using a car, so the difference is so massive that the rest of it becomes almost insignificant for many customers."
HDS doesn't sell specifically designated all-flash arrays, although all of the company's products can be purchased and deployed in flash-only mode. Madaio said the company has shipped all-flash high-end Virtual Storage Platform (VSP) arrays, but the entry-level enterprise HUS VM is the most logical product for broad all-flash use cases.
"We can ship a 600 TB flash system today with VSP with no issue, but the use cases for 600 TB of flash in one system are relatively small," Madaio said. "We don't find most customers looking and thinking of big enterprise systems in all-flash perspective. That's the reason we didn't really go there."
But one potential advantage HDS has is integration across its product lines. For instance, users can replicate between HUS VM and VSP through native replication in both products.
Another differentiator is the Hitachi Universal Volume Manager external storage virtualization software, which enables a user to view and manage the storage environment as a single pool. The software can also assist with data migration between Hitachi arrays or between Hitachi arrays and third-party storage.
Customers have the option to upgrade HUS VM from an all-flash to a tiered hybrid system with a combination of hard-disk drives (HDDs), solid-state drives (SSDs) and Hitachi's FMDs. They can also upgrade to a unified system with the addition of Hitachi NAS for network file services.
HUS VM supports block, file and object storage. The product is also among the most feature-rich all-flash options with support for capabilities such as thin provisioning, inline deduplication, snapshots, clones, data encryption and replication. Hitachi recently added three-data-center replication through a fee-based Remote Replication Extended software package.
List pricing for an all-flash HUS VM starts at $304,570 for 64 GB of cache and four 1.6 TB flash modules. HDS claims a $20 per GB list price for an array with 96 1.6 TB flash modules and $0.73 per IOPS for an array with 16 1.6 TB flash modules.
HUS VM's all-flash customers include Infosys, a consulting, technology and outsourcing firm, and Matiq, a major food supplier in Norway.