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Thursday, August 23, 2012
Hitachi Data Systems Announces Flash Strategy, Faster SSD Controller
Hitachi Data Systems (HDS) today announced its strategy for incorporating flash technology across the IT stack, along with a flash acceleration feature available today for Hitachi Virtual Storage Platform (VSP) that enables it to achieve more than 1,000,000+ random read IOPS.
Historically, the major inhibitor for the adoption of flash SSDs (solid-state drives) in the enterprise storage space has been the relative higher cost of SSDs versus HDDs (hard disk drives) and the durability of SSDs versus HDDs.
HDS believes that price is not the only consideration when it comes to using HDDs or MLC flash in the enterprise space, identifying durability as a major concern in such demanding environments. Flash vendors are addressing the durability of flash drives with wear leveling, and aggressive sparing within the drive and may specify a 5-year life but only under certain conditions (e.g.no more than 10 times the capacity of the drive written per day). However, HDS says that enterprise storage cannot be limited to such conditions so the enterprise control unit must add additional durability and preemptive maintenance features to raise flash SSD endurance levels to the level of HDDs.
Another concern is performance, especially when many users must share the SSD across an external shared bus controller in an enterprise system versus an SSD that is dedicated to a single user over an internal connection, as you would find in consumer products like a smart phone. While the SSD is much faster than a mechanical HDD, bottlenecks can occur within the drive as writes/formats increase and space becomes fragmented. Bottlenecks also occur in traditional enterprise controllers, which were designed for mechanical spinning disks and may not be prepared to handle the transfer speeds of an SSD. In order to get the optimum performance from SSDs, the enterprise storage controller must be enhanced for SSDs while maintaining all the functionality that has been developed over the years.
"In other words we must avoid the rip and replace of current storage controllers to implement the improvements that are required to realize the performance benefits of an SSD," says HDS' Hu Yoshida.
HDS believes that flash is ready for enterprise prime time where random performance is a key requirement. The current price gap between flash SSDs and HDDs can be reduced with the use of MLC flash, which has 2 bits per cell versus one for SLC (single-level cell) flash. This reduces the cost per bit by about 30%. Features like HDT (Hitachi Dynamic Tiering) can optimize the use of flash by moving only the hot pages of a volume into a flash tier while the cold pages migrate down to lower cost HDD tiers. In addition, HDP (Hitachi Dynamic Provisioning) increases durability by providing global wear leveling, which supplements the wear leveling within the drives to avoid hotspots.
HDS says that the new flash acceleration feature announced today for VSP raises its scalability limits by up to 3 times, doubles the scalability of HDP, increases virtual storage director (VSD) random I/O throughput and lowers I/O response times by up to 65%. Flash device throughput is increased with higher thread count scalability. With more than 24 threads running against an all SSDs configuration HDS has measured 1,000,000+ IOPs using 8K random reads.
This flash acceleration feature comes with a microcode upgrade to V04A. Overall, the total maximum throughput of VSP with V04A and flash acceleration will exceed 1,000,000 IOPS, according to HDS.
This feature is available today with VSP microcode V04A for open systems. HDS is offering this feature with a 120 day free trial.
For those considering the use of flash drives, this enhanced performance combined with the price of MLC flash from HDS makes the use of flash more affordable than previous SLC flash configurations.
Yoshida claims that the cost of MLC flash along with the performance acceleration of flash acceleration on VSP brings the cost down dramatically compared to previous SLC flash offerings, making flash media affordable on all VSP configurations.
"The wear leveling capabilities of HDP and HDT, combined with RAID protection and preemptive sparing available with VSP, can assure the durability of MLC flash for prime time," he added.
According to Roberto Basilio, vice president of Infrastructure Platforms Product Management at HDS,
Hitachi will also release its own flash controller.
Although he would not disclose when it will ship, but said the company will release more information in the next quarter.
What HDS would say about the controller is that it expects it to increase sustained read/write throughput on SSDs in its arrays by four times current generation SSDs based on multi-level cell (MLC) flash.
Like other flash controllers, Basilio said Hitachi's will optimize the way data is written to SSDs or PCIe flash cards, reducing the wear and extending the overall endurance of the drives.
The new controller will also offer secure data erase capability, meaning overwriting data several times, along with inline block data compression.