Flash memory is finding its way into more storage systems, augmenting and sometimes replacing slower digital storage technology, such as hard disk drives. As flash memory gets less expensive per GB, decisions to use flash memory where speed matters are more and more attractive. At the 2014 Storage Visions Conference John Scaramuzzo of SanDisk gave compelling arguments why flash memory will become more and more common in future storage systems, becoming an important element in every enterprise storage tier. Coughlin Associates puts on the annual Storage Visions Conference, held January 5 -6, 2014 in Las Vegas. Tom Coughlin is also the general chairman of the annual Flash Memory Summit.
A range of flash products has been and will be introduced, providing tiers of storage using flash memory. These include DIMM based flash memory that use the very fast memory bus of a computer system at the highest performance end (providing non-volatile solutions with less than 5 microsecond latency to a market segment that has been primarily DRAM until now), PCIe products for 10’s of microsecond latency and solid state drives with somewhat slower data rates and latencies (100’s of microseconds). This is much faster than HDDs which provide millisecond latencies.
SanDisk’s announcement that their UlltraDIMM product is being used in the IBM X3850 X6 Server (the product behind the recently announced IBM eXFlash DIMM) highlights the need to include non-volatile memory as a key element in future computer architectures. The IBM eXFlash DIMM offers 5-10 microsecond write latency with up to 12.8 TB non-volatile storage capacities.
John Scaramuzzo said that that IT demands are transforming the IT industry towards all flash data centers. IT trends include virtualization, In-Memory Computing, private and public clouds and $/GB replaced by total cost of ownership (TCO). These trends are driving the need for instant access and non-volatile memory. Factors that are making flash memory attractive from a TCO point of view are reduced power and cooling needs, reduced rack and floor space to achieve high performance with fewer servers and storage arrays.
Scaramuzzo’s talk and the recent SanDisk announcement focused on the particular advantages of DIMM-based flash memory that creates non-volatile memory on the computer memory bus. SanDisk demonstrated it’s advantages for high frequency trading and showed how using DIMM flash with SSDs can provide a 57% cost advantage for Virtual Desktop Consolidation vs. PCIe and DRAM.
The ULLtraDIMM technology enables in-memory computing, reducing the need to use traditional storage or PCIe interfaces for page swaps since a significant amount of content can be stored on the non-volatile ULLtraDIMM flash cards. Furthermore, like DRAM DIMMS, ULLtraDIMM cards can be distributed throughout a computer architecture wherever it is needed in order to reduce latency and speed content delivery. ULLtraDIMM modules are said to support low latencies even with high I/O workloads and they avoid the variable and unpredictable latencies often found in PCIe and storage interfaces due to the overhead of the additional interfaces as well as difficulties of sharing computing resources with PCIe or storage interfaces.
With regard to the value of PCIe storage versus traditional HDD arrays used for high performance applications, a group of 50 SSDs providing a Database Management System for close to the same capital costs provided significantly lower operating costs than a 336 (300 GB) HDD system, providing an over all performance cost of $0.03/IOPS compared to $0.73/IOPS.
Scaramuzzo indicated that while today, flash is replacing HDDs for hot data, in the next wave of storage systems flash will begin to replace HDDs and magnetic tape for cooler data as well. Jason Taylor from Facebook indicated that this could happen in a keynote talk at the 2013 Flash Memory Summit). According to SanDisk, with the introduction of 3D flash memory the total cost of ownership of flash for colder storage will approach those of HDDs because technology is advancing so much faster for flash memory than HDDs—and thus we could end up ultimately with an all flash data center.