Hybrid HDDs

HDD & SSD Combined Into One

Wafer Scale HDDThe SSD Guy has often explained to readers that the storage industry is caught between two alternatives:  fast and costly, or cheap and slow.  This is the key difference between SSDs and HDDs.  I have recently learned of a new secret government research effort, code named “SiliDisk,” that will provide the best of both worlds by marrying flash memory with the mechanics of an HDD.

The approach is incredibly ingenious, while remaining deceptively simple: All that is required is to replace the disks in an HDD with the wafers used to manufacture NAND flash.  Both are round, so there’s little engineering effort to switch from a magnetic disk to a flash wafer.

The NAND flash on the wafer is almost completely standard.  The only two changes are that the chips aren’t scribed or sawn apart, saving a small sum, but a hole must be etched through the center (which can be seen in the photo below) offsetting this savings.  The HDD mechanisms are unchanged with one exception: While today’s HDDs are largely manufactured using 2.5″ and 3.5″ platters (65mm & 90mm), NAND flash is exclusively produced on 300mm wafers.  This means that Continue reading

Intel’s Optane: Two Confusing Modes. Part 2) Memory Mode

Exploding HeadThis post is the second part of a four part series in The SSD Guy blog to help explain Intel’s two recently-announced modes of accessing its Optane DIMM, formally known as the “Intel Optane DC Persistent Memory.”

Memory Mode

The most difficult thing to understand about the Intel Optane DC Persistent Memory when used in Memory Mode is that it is not persistent.  Go back and read that again, because it didn’t make any sense the first time you read it.  It didn’t make any sense the second time either, did it?

Don’t worry.  This is not really important.  The difficulty stems from Intel’s marketing decision to call Optane DIMMs by the name “Intel Optane DC Persistent Memory.”  Had they simply called them “Optane DIMMs” like everyone expected them to then there would have been Continue reading

Intel’s Optane: Two Confusing Modes. Part 1) Overview

Exploding HeadIntel recently announced two operating modes for the company’s new Optane DIMMs, formally known as “Intel Optane DC Persistent Memory.”  The company has been trying to help the world to understand these two new operating modes but they are still pretty baffling to most of the people The SSD Guy speaks to.  Some say that the concepts make their heads want to explode!

How does Optane’s “Memory Mode” work?  How does “App Direct” Mode work?  In this four-part series will try to provide some answers.

Like all of my NVDIMM-related posts, this series challenges me with the question: “Should it be published in The SSD Guy, or in The Memory Guy?”  This is a point of endless confusion for me, since NVDIMM and Intel’s Optane blur the lines between Memory and Storage.  I have elected to post this in The SSD Guy with the hope that it will be found by readers who want to understand Optane for its storage capabilities.

Memory Mode is the easy sell for the short term.  It works with all current application software without modification.  It just makes it look like you have a TON of DRAM.

App Direct Mode is really cool if Continue reading

Podcast: Flash Memory Summit

GreybeardsThose of you who enjoy listening to podcasts may want to hear Ray Lucchesi (Silverton Consulting) and Howard Marks (Deep Storage) interview me for their series “Greybeards on Storage.”

This interview is their 70th episode covering the world of storage.  These guys do a fantastic job of probing this industry with great enthusiasm and insight.

This episode is a 42-minute compendium of the sights and goings-on at last August’s Flash Memory Summit along with a number of side trips into the world of SSDs and memory chips.  It’s not strictly structured, and not strictly serious, but just three industry insiders having a lot of fun sharing their observations.

Some of the broad range of subjects that we Continue reading

Intel Announces Optane SSDs for the Enterprise

Intel-Optane-SSDThis week Intel announced the Optane SSD DC P4800X Series, new enterprise SSDs based on the company’s 3D XPoint memory technology which Intel says is the first new memory technology to be introduced since 1989.  The technology was introduced to fill a price/performance gap that might impede Intel’s sales of high-performance CPUs.

Intel was all aglow with the promise of performance, claiming that the newly-released SSDs offer: “Consistently amazing response time under load.”

Since the early 1990s Intel has realized that it needs for the platform’s performance to keep pace with the ongoing performance increases of its new processors.  A slow platform will limit the performance of any processor, and if customers don’t see any benefit from purchasing a more expensive processor, then Intel will be unable to keep its processor prices high.

Recently NAND flash SSDs have helped Intel to improve the platform’s speed, as did the earlier migration of Continue reading

Flash vs. DRAM in PCs – Flash Wins

Chart from Objective Analysis report: How PC NAND will Undermine DRAMSome time ago Objective Analysis ran nearly 300 standard benchmarks on a PC with varying amounts of flash and DRAM and found that a dollar’s worth of flash provided a greater performance boost than a dollar’s worth of DRAM once the DRAM size grew above a certain minimum (1-2GB) depending on the benchmark.

You might wonder how this could possibly be true.  Everyone knows that best way to improve any computing system’s performance is to add DRAM main memory.  How could flash, which is orders of magnitude slower than DRAM, provide a bigger performance boost than DRAM?

It all makes sense if you think of the DRAM of something that is there only to make the HDD look faster.  More is better, but if you can use a little less DRAM and add a large flash memory layer then disk accesses appear to speed up even more.

The benchmark data and the price/performance findings that are Continue reading

IBM Software + SanDisk Hardware

One of SanDisk's InfiniFlash BoardsIn a joint press release, SanDisk and IBM announced support for each other’s products.  The IBM Spectrum Scale filesystem will support SanDisk’s InfiniFlash all-flash array to provide a high-capacity high-speed software-defined storage system.

At first glance this may seem a little odd, since IBM sells its own all-flash array, the FlashSystem, which became an IBM product line when the company acquired Texas Memory Systems (TMS) back in 2012.  That is not the case, though.  IBM has been validating that its Spectrum Storage products will work with just about any storage type that its customers may want to use.  Rather than narrowing this software’s support to only IBM storage systems, IBM is showing that Spectrum Scale is flexible enough to work with a multitude of solutions, supporting InfiniFlash the same as it does other internal server capacity and other external storage in the form of JBODs (“Just a Bunch of Disks”) or JBOFs (“Just a Bunch of Flash”).

In this case IBM has worked with SanDisk to validate that its Spectrum Scale storage management software works with InfiniFlash, just as it does with those many other storage solutions.

In the announcement IBM explains that Continue reading

Hybrid Drives Not Catching On

Seagate Momentus SSHD press photoSeagate announced last week that the company had shipped a total of 10 million Solid State Hybrid Drives (SSHDs) over the lifetime of the product.  This is far short of expectations by The SSD Guy and a number of other analysts and industry participants.

Why were our expectations higher?  There were a few reasons:

  • The hybrid drive can be viewed as an evolution of the DRAM cache already incorporated into nearly all HDDs today.  Replacing or augmenting an expensive DRAM cache with a slower, cheaper NAND cache makes a lot of sense.
  • An SSHD performs significantly better than Continue reading

IBM Adds Server-Side Caching

IBM's FlashCache Server-Side Caching SoftwareIBM today announced its FlashCache Storage Accelerator, a software product that supports flash caching in a broad range of systems.  FlashCache operates over three families of IBM servers (System x, BladeCenter and Flex System) and a variety of flash types to accelerate any back-end storage, including non-IBM storage arrays.

Although the cache’s data is dynamically updated to match the random workloads of virtualized systems (i.e. to accelerate VMware), it also improves the performance of Windows and Linux environments.

The cache uses a Write Through policy to solve a number of Continue reading

White Paper: Using Flash as Memory

DRAM, Flash, and HDD HierarchyToday NAND flash is being shoehorned into HDD formats simply because it is persistent – the data doesn’t disappear when the lights go out.  This approach fails to take advantage of NAND’s greatest strength – its low cost relative to DRAM – and this prevents it from fully meeting the needs of most data centers.

Since 2004 NAND has been cheaper than DRAM, and today its price per gigabyte is an order of magnitude lower than that of DRAM.  NAND is cheaper and slower than DRAM, and HDD is cheaper and slower than NAND.

A role better suited to NAND flash technology is Continue reading