Jim O'Reilly


Upcoming Events

Where the Cloud Touches Down: Simplifying Data Center Infrastructure Management

Thursday, July 25, 2013
10:00 AM PT/1:00 PM ET

In most data centers, DCIM rests on a shaky foundation of manual record keeping and scattered documentation. OpManager replaces data center documentation with a single repository for data, QRCodes for asset tracking, accurate 3D mapping of asset locations, and a configuration management database (CMDB). In this webcast, sponsored by ManageEngine, you will see how a real-world datacenter mapping stored in racktables gets imported into OpManager, which then provides a 3D visualization of where assets actually are. You'll also see how the QR Code generator helps you make the link between real assets and the monitoring world, and how the layered CMDB provides a single point of view for all your configuration data.

Register Now!

A Network Computing Webinar:
SDN First Steps

Thursday, August 8, 2013
11:00 AM PT / 2:00 PM ET

This webinar will help attendees understand the overall concept of SDN and its benefits, describe the different conceptual approaches to SDN, and examine the various technologies, both proprietary and open source, that are emerging. It will also help users decide whether SDN makes sense in their environment, and outline the first steps IT can take for testing SDN technologies.

Register Now!

More Events »

Subscribe to Newsletter

  • Keep up with all of the latest news and analysis on the fast-moving IT industry with Network Computing newsletters.
Sign Up

See more from this blogger

Hybrid DIMMs And The Quest For Speed

With an apparently insatiable need for I/O performance and near-line storage, the industry has produced a couple of flash products that use a DIMM model in the search for speed.

Using the memory bus as a means to access flash makes for a low-latency pathway and creates a storage technology faster than any PCIe solution on the market. This is what SanDisk and Diablo did with their UltraDIMM technology, and it allows a tighter coupling between the app and data with an option to bypass the OS storage stack.

Using UltraDIMMs as a flash accelerator in place of a PCIe solution is attractive, and one reason IBM recently announced servers with UltraDIMMs. These designs achieve five microsecond latency and IBM’s target market for the technology is in-memory databases, where this is a crucial issue. Most importantly, that latency is sustained consistently under high workloads and with the memory scaled out to large configurations, which is important in financial applications. PCIe devices start at 20 microsecond latencies and slow down under high I/O loads, with much more erratic latencies that can reach milliseconds.

Performance per UltraDIMM is 1GB/sec for sequential reads, which increases almost linearly with the number of DIMMs installed. At 400GB, the DIMM’s capacity is smaller than PCIe flash accelerators, but capacity can be increased by having multiple units, to as much as 12.8Tb in the IBM systems, for instance. In a test with 10,000 VDIs, SanDisk reports having doubled the number of VMs it could service in a server compared with PCIe SSD, and this more than halved the cost of the deployment.

The SanDisk-Diablo approach is relatively easy to integrate into servers, though BIOS extensions and drivers are required.

[Read Howard Marks' analysis of Diablo Technologies' Memory Channel Storage devices in "Putting Flash On The Memory Bus."]

Viking Technology took a different tack. It has created a DRAM backed up by flash memory. Viking's ArxCis product is effectively a non-volatile DRAM. As such, atomic reads and writes take the same time as in normal DRAM, and block I/O is completely avoidable. It’s possible to operate on the memory with standard CPU commands and write a single byte if desired.

ArxCis-NV (image below) has built-in logic to detect power failure or turn-off, and stores the data in the DRAM into flash built onto the same DIMM. When power is restored, the data is returned to the DRAM on the DIMM. This makes the memory persistent NVDRAM, so it is a distinct use case to the UltraDIMM.

Viking has partnered with SuperMicro to match motherboards. BIOS changes allow register and cache protection, while the OS and other software need changes to recognize persistence. Currently, this fits appliance designs really well, since the code is proprietary. We can expect to see the technology in storage systems soon.

An NVDRAM has major implications for the operating system and the BIOS if it is to be used to its full capability. At its simplest, it can be a RAMDisk just as the UltraDIMM, with even higher throughput and much faster random access. A bit of work on the OS can make it word-addressable, which is even faster, with latencies around 30 nanoseconds.

Going the next step and melding the non-volatile memory into applications requires changes to compilers and link editors, and apps need modification to recognize the persistent space as mapped to variables etc. This is a major effort requiring multiple vendors to work together.

The Storage Networking Industry Association (SNIA) has set up an NVDIMM SIG to focus efforts on the system and software changes required. "NVDIMM brings new capabilities to systems, and is a mechanism for enabling next-generation storage-class memories,” Adrian Proctor, the SIG chair and VP of marketing for Viking said in an interview.

The flash-based DIMM products from Viking and SanDisk are useful, even powerful, steps along a path to new persistent memory technologies. These flash-based DIMMs offer, on the one hand, a performance boost for existing server solutions, and on the other, a new type of tool that looks to expand how systems are built, how they recover from failures, and ultimately, to provide a super-fast alternative to file and block I/O.

Related Reading

More Insights

Network Computing encourages readers to engage in spirited, healthy debate, including taking us to task. However, Network Computing moderates all comments posted to our site, and reserves the right to modify or remove any content that it determines to be derogatory, offensive, inflammatory, vulgar, irrelevant/off-topic, racist or obvious marketing/SPAM. Network Computing further reserves the right to disable the profile of any commenter participating in said activities.

Disqus Tips To upload an avatar photo, first complete your Disqus profile. | Please read our commenting policy.
Vendor Comparisons
Network Computing’s Vendor Comparisons provide extensive details on products and services, including downloadable feature matrices. Our categories include:

Research and Reports

Network Computing: April 2013

TechWeb Careers