by Marty Foltyn

Persistent memory discussions are capturing the minds of SNIA members and colleagues.  At last month’s SNIA Storage Developer Conference, NVM (non-volatile memory) and NVMe sessions were standing-room-only, and opinion sharing continued into animated hallway discussions.  I encourage you to check out the many presentations on the SNIA SDC website, and to download the live recordings of the keynotes here.

SNIA continued their education on persistent memory at this week’s Memcon in Santa Clara CA. SNIA’s booth was packed with attendees asking questions like what is the difference between the different kinds of NVDIMMs (you’ll want to check out our new snia_nvdimm_infographic), and is NVDIMM a standard (indeed, it is, JEDEC just released the DDR4 NVDIMM-N Design Standard Revision 1.0 last month, and you can download the link from our website).

The work being done within SNIA on persistent memory is contributing to a seachange in the industry – the convergence of memory and storage – perhaps the most revolutionary change since the invention of the transistor more than 60 years ago.  To learn more, check out this interview with Jim Pappas, SNIA’s Vice-Chairman and co-chair of the SNIA Solid State Storage Initiative.  And mark your calendar for January 18, 2017, when SNIA will hold the 5th annual Persistent Memory Summit in San Jose CA.  The latest details can be found here.

 

 

SNIA and the Solid State Storage Initiative (SSSI) invite you to join them at Flash Memory Summit 2016, August 8-11 at the Santa Clara Convention Center. SNIA members and colleagues receive $100 off any conference package using the code "SNIA16" by August 4 when registering for Flash Memory Summit at http://www.flashmemorysummit.com On Monday, August 8, from 1:00pm – 5:00pm, a SNIA Education Afternoon will be open to the public in SCCC Room 203/204, where attendees can learn about multiple storage-related topics with five SNIA Tutorials on flash storage, combined service infrastructures, VDBench, stored-data encryption, and Non-Volatile DIMM (NVDIMM) integration from SNIA member speakers. Following the Education Afternoon, the SSSI will host a reception and networking event in SCCC Room 203/204 from 5:30 pm - 7:00 pm with SSSI leadership providing perspectives on the persistent memory and SSD markets, SSD performance, NVDIMM, SSD data recovery/erase, and interface technology. Attendees will also be entered into a drawing to win solid state drives. SNIA and SSSI members will also be featured during the conference in the following sessions:

• Persistent Memory (Preconference Session C) NVDIMM presentation by Arthur Sainio, SNIA NVDIMM SIG Co-Chair (SMART Modular) Monday, August 8, 8:30am- 12:00 noon 
• Data Recovery of SSDs (Session 102-A) SIG activity discussion by Scott Holewinski, SSSI Data Recovery/Erase SIG Chair (Gillware) Tuesday, August 9, 9:45 am - 10:50 am
• Persistent Memory – Beyond Flash sponsored by the SNIA SSSI (Forum R-21) Chairperson: Jim Pappas, SNIA Board of Directors Vice-Chair/SSSI Co-Chair (Intel); papers presented by SNIA members Rob Peglar (Symbolic IO), Rob Davis (Mellanox), Ken Gibson (Intel), Doug Voigt (HP), Neal Christensen (Microsoft) Wednesday, August 10, 8:30 am - 11:00 am
• NVDIMM Panel, organized by the SNIA NVDIMM SIG (Session 301-B) Chairperson: Jeff Chang SNIA NVDIMM SIG Co-Chair (AgigA Tech); papers presented by SNIA members Alex Fuqa (HP), Neal Christensen (Microsoft) Thursday, August 11, 8:30am - 9:45am

Finally, don't miss the SNIA SSSI in Expo booth #820 in Hall B and in the Solutions Showcase in Hall C on the FMS Exhibit Floor. Attendees can review a series of updated performance statistics on NVDIMM and SSD, see live NVDIMM demonstrations, access SSD data recovery/erase education, and preview a new white paper discussing erasure with regard to SSDs. SNIA representatives will also be present to discuss other SNIA programs such as certification, conformance testing, membership, and conferences.

SNIA and the Solid State Storage Initiative (SSSI) invite you to join them at Flash Memory Summit 2016, August 8-11 at the Santa Clara Convention Center. SNIA members and colleagues receive $100 off any conference package using the code “SNIA16” by August 4 when registering for Flash Memory Summit at http://www.flashmemorysummit.com

On Monday, August 8, from 1:00pm – 5:00pm, a SNIA Education Afternoon will be open to the public in SCCC Room 203/204, where attendees can learn about multiple storage-related topics with five SNIA Tutorials on flash storage, combined service infrastructures, VDBench, stored-data encryption, and Non-Volatile DIMM (NVDIMM) integration from SNIA member speakers.

Following the Education Afternoon, the SSSI will host a reception and networking event in SCCC Room 203/204 from 5:30 pm – 7:00 pm with SSSI leadership providing perspectives on the persistent memory and SSD markets, SSD performance, NVDIMM, SSD data recovery/erase, and interface technology. Attendees will also be entered into a drawing to win solid state drives.

SNIA and SSSI members will also be featured during the conference in the following sessions:

• Persistent Memory (Preconference Session C)
  NVDIMM presentation by Arthur Sainio, SNIA NVDIMM SIG Co-Chair (SMART Modular)
  Monday, August 8, 8:30am- 12:00 noon 
• Data Recovery of SSDs (Session 102-A)
  SIG activity discussion by Scott Holewinski, SSSI Data Recovery/Erase SIG Chair (Gillware)
  Tuesday, August 9, 9:45 am – 10:50 am
• Persistent Memory – Beyond Flash sponsored by the SNIA SSSI (Forum R-21) Chairperson: Jim Pappas, SNIA Board of Directors Vice-Chair/SSSI Co-Chair (Intel); papers presented by SNIA members Rob Peglar (Symbolic IO), Rob Davis (Mellanox), Ken Gibson (Intel), Doug Voigt (HP), Neal Christensen (Microsoft) Wednesday, August 10, 8:30 am – 11:00 am
• NVDIMM Panel, organized by the SNIA NVDIMM SIG (Session 301-B) Chairperson: Jeff Chang SNIA NVDIMM SIG Co-Chair (AgigA Tech); papers presented by SNIA members Alex Fuqa (HP), Neal Christensen (Microsoft) Thursday, August 11, 8:30am – 9:45am

Finally, don’t miss the SNIA SSSI in Expo booth #820 in Hall B and in the Solutions Showcase in Hall C on the FMS Exhibit Floor. Attendees can review a series of updated performance statistics on NVDIMM and SSD, see live NVDIMM demonstrations, access SSD data recovery/erase education, and preview a new white paper discussing erasure with regard to SSDs. SNIA representatives will also be present to discuss other SNIA programs such as certification, conformance testing, membership, and conferences.

Is your head spinning with all the variations in solid state storage technologies, interconnects, and application level approaches on the market today?

Then you will want to mark your professional calendar – at YOUR convenience – to watch the SNIA BrighTalk webcast: Architectural Principles for Networked Solid State Storage Access,” – one of the most successful ever produced by SNIA!

In this on-demand webcast, SNIA Ethernet Storage Forum and Solid State Storage Initiative experts J Metz, SNIA Board member from Cisco, and Doug Voigt, chair of the SNIA NVM Programming Technical Working Group and a member of the SNIA Technical Council, deliver the answers to questions like these:

• How do applications see IO and memory access differently?
• What is the difference between a memory and an SSD technology?
• How do application and technology views permute?
• How do memory and network interconnects change the equation?
• What are persistence domains and why are they important?

Over 650 professionals have viewed this session – and now it is available for you free of charge on-demand!

Bookmark this link now and plan a great “desktop lunch” session all your own to learn the latest on the application of networked solid state technologies (and maybe you’ll even mention it to your colleagues)!

 

 

The recent NVDIMM webcasts on the SNIA BrightTALK Channel sparked many questions from the almost 1,000 viewers who have watched it live or downloaded the on-demand cast. Now,  NVDIMM SIG Chairs Arthur Sainio and Jeff Chang answer 35 of them in this blog.  Did you miss the live broadcasts? No worries, you can view NVDIMM and other webcasts on the SNIA webcast channel https://www.brighttalk.com/channel/663/snia-webcasts.

FUTURES QUESTIONS

What timeframe do you see server hardware, OS, and applications readily adopting/supporting/recognizing NVDIMMs?

DDR4 server and storage platforms are ready now. There are many off-the shelf server and/or storage motherboards that support NVDIMM-N.

Linux version 4.2 and beyond has native support for NVDIMMs. All the necessary drivers are supported in the OS.

NVDIMM adoption is in progress now.

Technical Preview 5 of Windows Server 2016 has NVDIMM-N support
 

How, if at all, does the positioning of NVDIMM-F change after the eventual introduction of new NVM technologies?

If 3DXP is successful it will likely to have a big impact on NVDIMM-F. 3DXP could be seen as an advanced version of a NVDIMM-F product. It sits directly on the DDR4 bus and is byte addressable.

NVDIMM-F products have the challenge of making them BYTE ADDRESSBLE, depending on what kind of persistent media is used.

If NAND flash is used, it would take a lot of techniques and resources to make such a product BYTE ADDRESSABLE.

On the other hand, if the new NVM technologies bring out persistent media that are BYTE ADDRESSABLE then the NVDIMM-F could easily use them for their backend.
How does NVDIMM-N compare to Intel’s 3DXPoint technology?

At this point there is limited technical information available on 3DXP devices.

When the specifications become available the NVDIMM SIG can create a comparison table.

NVDIMM-N products are available now. 3DXP-based products are planned for 2017, 2018. Theoretically 3DXP devices could be used on NVDIMM-N type modules

 

 

 

PERFORMANCE AND ENDURANCE QUESTIONS

What are the NVDIMM performance and endurance requirements?

NVDIMM-N is no different from a RDIMM under normal operating conditions. The endurance of the Flash or NVM technology used on the NVDIMM-N is not a critical factor since it is only used for backup.

NVDIMM-F would depend on various factors: (1) is the backend going to be NAND Flash or some other entity? (2) What kind of access pattern is going to be done by the application? The performance must be at least same as that of NVDIMM-N.

Are there endurance requirements for NVDIMM-F? Won’t the flash wear out quickly when used as memory?

Yes, the aspect of Flash being used as a RANDOM access device with MEMORY access characteristics would definitely have an impact on the endurance.
NVDIMM-F – Doesn’t the performance limitations of the NAND vs. DRAM effect the application?

NAND Flash would never hit the performance requirements of the DRAM when seen as an entity to entity comparison. But, in the whole perspective of a wider solution, the data path of DRAM data -> Persistence Data in a traditional model would have more delays contributed by a good number of software layers involved in making the data persistent versus, in the NVDIMM-F the data that is instantly persistent — for just a short term additional latency.
Is there extra heat being generated….does it need any other cooling (NVDIMM-F, NVDIMM-N)

No
In general, our testing of NVDIMM-F vs PCIe based SSDs has not shown the expected value of NVDIMMs.  The PCIe based NVMe storage still outperforms the NVDIMMs.

TBD
What is the amount of overhead that NVDIMMs are adding on CPUs?

None at normal operation
What can you say about the time required typically to charge the supercaps?  Is the application aware of that status before charge is complete?

Approximately two minutes depending on the density of the NVDIMM and the vendor.

The NVDIMM will not be ready because the charging status and in turn the system BIOS will wait; until it times out if the NVDIMM is not functioning.

USE QUESTIONS

What will happen if a system crashes then comes back before the NVDIMM finishes backup? How the OS know what to continue as the state in the register/L1/L2/L3 cache is already lost?

When system comes back up, it will check if there is valid data backed up in the NVDIMM. If yes, backed up data will be restored first before the BIOS sets up the system.

The OS can’t depend on the contents of the L1/L2/L3 cache. Applications must do I/O fencing, use commit points, etc. to guarantee data consistency.

Power supply should be able to hold power for at least 1ms after the warning of AC power loss.

Is there garbage collection on NVDIMMs?

This depends on individual vendors. NVDIMM-N may have overprovisioning and wear levering management for the NAND Flash.

Garbage collection really only makes sense for NVDIMM-F.
How is byte addressing enabled for NAND storage?

By default, the NAND storage can be addressed only through the BLOCK mode addressing. If BYTE addressability is desired, then the DDR memory at the front must provide sophisticated CACHING TECHNIQUES to trick the Host Memory Controller in to thinking that it is actually accessing a larger capacity DDR memory.
Is the restore command issued over the I2C bus?  Is that also known as the SMBus?

Yes, Yes
Could NVDIMM-F products be used as both storage and memory within the same server?

NVDIMM-F is by definition only block storage. NVDIMM-P is both (block) storage and memory.

 

COMPATIBILITY QUESTIONS

 

Is NVDIMM-N support built into the OS or do the NVDIMM vendors need to provide drivers? What OS’s (Windows version, Linux kernel version) have support?

In Linux, right from 4.2 version of the Kernel, the generic NVDIMM-N support is available.

All the necessary drivers are provided in the OS itself.

Regarding the Linux distributions, only Fedora and Ubuntu have upgraded themselves to the 4.x kernel.

The crucial aspect is, the BIOS/MRC support needed for the vendor specific NVDIMM-N to get exposed to the Host OS.

MS Windows has OS support – need to download.
What OS support is available for NVDIMM-F? I’m assuming some sort of drivers is required.

Diablo has said they worked the BIOS vendors to enable their Memory1 product. We need to check with them.

For other NVDIMM-F vendors they would likely require drivers.

As of now no native OS support is available.
Will NVDIMMs work with typical Intel servers that are 2-3 years old?   What are the hardware requirements?

The depends on the CPU. For Haswell, Grantley, Broadwell, and Purley the NVDIMM-N are and/or will be supported

The hardware requires that the CPLD, SAVE, and ADR signals are present

Is RDMA compatible with NVDIMM-F or NVDIMM-N?

The RDMA (Remote Direct Memory Access) is not available by default for NVDIMM-N and NVDIMM-F.

A software layer/extension needs to be written to accommodate that. Works are in progress by the PMEM committee (www.pmem.io) to make the RDMA feature available transparently for the applications in the future.

SNIA Reference: http://www.snia.org/sites/default/files/SDC15_presentations/persistant_mem/ChetDouglas_RDMA_with_PM.pdf
What’s the highest capacity that an NVDIMM-N can support?

Currently 8GB and 16GB but this depends on individual vendor’s roadmaps.

 

COST QUESTIONS

What is the NVDIMM cost going to look like compared to other flash type storage options?

This relates directly to what types and quantizes of Flash, DRAM, controllers and other components are used for each type.

 

MISCELLANEOUS QUESTIONS

How many vendors offer NVDIMM products?

AgigA Tech, Diablo, Hynix, Micron, Netlist, PNY, SMART, and Viking Technology are among the vendors offering NVDIMM products today.

 

Is encryption on the NVDIMM handled by the controller on the NVDIMM or the OS?

Encryption on the NVDIMM is under discussion at JEDEC. There has been no standard encryption method adopted yet.

If the OS encrypts data in memory the contents of the NVDIMM backup would be encrypted eliminating the need for the NVDIMM to perform encryption. Although because of the performance penalty of OS encryption, NVDIMM encryption is being considered by NVDIMM vendors.
Are memory operations what is known as DAX?

DAX means Direct Access and is the optimization used in the modern file systems – particularly EXT4 – to eliminate the Kernel Cache for holding the write data. With no intermediate cache buffers, the write operations go directly to the media. This makes the writes persistent as soon as they are committed.

Can you give some practical examples of where you would use NVDIMM-N, -F, and –P?

NVDIMM-N: load/store byte access for journaling, tiering, caching, write buffering and metadata storage

NVDIMM-F: block access for in-memory database (moving NAND to the memory channel eliminates traditional HDD/SSD SAS/PCIe link transfer, driver, and software overhead)

NVDIMM-P: can be used either NVDIMM-N or –F applications
Are reads and writes all the same latency for NVDIMM-F?

The answer depends on what kind of persistent layer is used.   If it is the NAND flash, then the random writes would have higher latencies when compared to the reads. If the 3D XPoint kind of persistent layer is used, it might not be that big of a difference.

 

I have interest in the NVDIMMs being used as a replacement for SSD and concerns about clearing cache (including credentials) stored as data moves from NVM to PM on an end user device

The NVDIMM-N uses serialization and fencing with Intel instructions to guarantee data is in the NVDIMM before a power failure and ADR.

 

I am interested in how many banks of NVDIMMs can be added to create a very large SSD replacement in a server storage environment.

NVDIMMs are added to a system in memory module slots. The current maximum density is 16GB or 32GB. Server motherboards may have 16 or 24 slots. If 8 of these slots have 16GB NVDIMMs that should be like a 96GB SSD.
What are the environmental requirements for NVDIMMs (power, cooling, etc.)?

There are some components on NVDIMMs that have a lower operating temperature than RDIMMs like flash and FPGA devices. Refer to each vendor’s data sheet for more information. Backup Energy Sources based on ultracapacitors require health monitoring and a controlled thermal environment to ensure an extended product life.
How about data-at-rest protection management? Is the data in NVDIMM protected/encrypted? Complying with TCG and FIPS seems very challenging. What are the plans to align with these?

As of today, encryption has not been standardized by JEDEC. It is currently up to each NVDIMM vendor whether or not to provide encryption..

 

Could you explain the relationship between the NVDIMM and the IO stack?

In the PMEM mode, the Kernel presents the NVDIMM as a reserved memory, directly accessible by the Host Memory Controller.

In the Block Mode, the Kernel driver presents the NVDIMM as a block device to the IO Block Layer.
With NVDIMMs the data can be in memory or storage. How is the data fragmentation managed?

The NVDIMM-N is managed as regular memory. The same memory allocation fragmentation issues and handling apply. The NVDIMM-F behaves like an SSD. Fragmentation issues on an NVDIMM-F are handled like an SSD with garbage collection algorithms.

 

Is there a plan to support PI type data protection for NVDIMM data? If not, achieving E2E data protection cannot be attained.

As of today, encryption has not been standardized by JEDEC. It is currently up to each NVDIMM vendor whether or not to provide encryption.

 

Since NVDIMM is still slower than DRAM so we still need DRAM in the system? We cannot get rid of DRAM yet?

With NVDIMM-N DRAM is still being used. NVDIMM-N operates at the speed of standard RDIMM

With NVDIMM-F modules, DRAM memory modules are still needed in the system.

With NVDIMM-P modules, DRAM memory modules are still needed in the system.
Can you use NVMe over ethernet?

NVMe over Fabrics is under discussion within SNIA http://www.snia.org/sites/default/files/SDC15_presentations/networking/WaelNoureddine_Implementing_%20NVMe_revision.pdf

 

April's Open Server Summit brought thought leaders together for two days of keynotes, sessions, and a demonstration showcase on converged server-storage-networking infrastructures and open specifications shaping the data center. SNIA board member Rob Peglar of Micron Technology delivered a keynote on new persistent memory directions that create new approaches for system architects. A Summit highlight was a SNIA's Solid State Storage Initiative sponsored panel on Providing Storage at Memory Speed Using NVDIMMs, where panelists reviewed how NVDIMMs operate in new interest areas for persistent memory like databases, Web 2.0, analytics, OLTP, and video and image processing. NVDIMM technologies were also featured on the showfloor with demonstrations from SNIA NVDIMM Special Interest Group (SIG) members Diablo Technologies, Netlist, and SMART Modular.  Download the presentation from Open Server Summit here. SNIA's NVDIMM SIG followed up the interest at Open Server Summit with a comprehensive webcast answering today's questions on NVDIMM and Non-Volatile Memory (NVM).  Jeff Chang, Co-Chair of the NVDIMM SIG from AgigA Tech, provided a quick refresh on NVDIMM types.  NVDIMM SIG member Mat Young from Netlist covered NVDIMM Performance Benchmarking.  Doug Voigt, Chair of the SNIA NVM Programming Technical Work Group from Hewlett Packard Enterprise, reviewed NVM Programming Model Updates, and Arthur Sainio, Co-Chair of the NVDIMM SIG from SMART Modular, wrapped up the session with answers to the NVDIMM questions raised at the January 2016 webcast and at Open Server Summit.  The webcast is now available for download on the SNIA BrightTALK channel at https://www.brighttalk.com/webcast/663/197009. Next up from the SNIA Solid State Storage Initiative will be a keynote and demonstration at May 23-24 In-Memory Computing Summit at the Grand Hyatt in San Francisco.  Join us there!

April’s Open Server Summit brought thought leaders together for two days of keynotes, sessions, and a demonstration showcase on converged server-storage-networking infrastructures and open specifications shaping the data center. SNIA board member Rob Peglar of Micron Technology delivered a keynote on new persistent memory directions that create new approaches for system architects.

A Summit highlight was a SNIA’s Solid State Storage Initiative sponsored panel on Providing Storage at Memory Speed Using NVDIMMs, where panelists reviewed how NVDIMMs operate in new interest areas for persistent memory like databases, Web 2.0, analytics, OLTP, and video and image processing. NVDIMM technologies were also featured on the showfloor with demonstrations from SNIA NVDIMM Special Interest Group (SIG) members Diablo Technologies, Netlist, and SMART Modular.  Download the presentation from Open Server Summit here.

SNIA’s NVDIMM SIG followed up the interest at Open Server Summit with a comprehensive webcast answering today’s questions on NVDIMM and Non-Volatile Memory (NVM).  Jeff Chang, Co-Chair of the NVDIMM SIG from AgigA Tech, provided a quick refresh on NVDIMM types.  NVDIMM SIG member Mat Young from Netlist covered NVDIMM Performance Benchmarking.  Doug Voigt, Chair of the SNIA NVM Programming Technical Work Group from Hewlett Packard Enterprise, reviewed NVM Programming Model Updates, and Arthur Sainio, Co-Chair of the NVDIMM SIG from SMART Modular, wrapped up the session with answers to the NVDIMM questions raised at the January 2016 webcast and at Open Server Summit.  The webcast is now available for download on the SNIA BrightTALK channel at https://www.brighttalk.com/webcast/663/197009.

Next up from the SNIA Solid State Storage Initiative will be a keynote and demonstration at May 23-24 In-Memory Computing Summit at the Grand Hyatt in San Francisco.  Join us there!

If you are in Silicon Valley or the Bay Area this week, SNIA welcomes you to join them and the Solid State Storage Initiative April 13-14 at the Santa Clara Convention Center for Open Server Summit 2016, the industry’s premier event that focuses on the design of next- generation servers with topics on data center efficiency, SSDs, core OS, cloud server design, the future of open server and open storage, and other efforts toward combining industry-standard hardware with open-source software.

The SNIA NVDIMM Special Interest Group is featured at OSS 2016, and will host a panel Thursday April 14 on NVDIMM technology, moderated by Bill Gervasi of JEDEC and featuring SIG members Diablo Technology, Netlist, and SMART Modular. The panel will highlight the latest activities in the three “flavors” of NVDIMM , and offer a perspective on the future of persistent memory in systems. Also, SNIA board member Rob Peglar of Micron Technology will deliver a keynote on April 14, discussing how new persistent memory directions create new approaches for system architects and enable entirely new applications involving enormous data sets and real-time analysis.

SSSI will also be in booth 403 featuring demonstrations by the NVDIMM SIG, discussions on SSD data recovery and erase, and updates on solid state storage performance testing.  SNIA members and colleagues can register for $100 off using the code SNIA at http://www.openserversummit.com.

The debate between hard drives and solid state drives goes on in 2016, particularly in the area of areal densities - the actual density of storage on a device.  Fortunately for us, Tom Coughlin, SNIA Solid State Storage Initiative Education Chair, and a respected analyst who contributes to Forbes, has advised that flash memory areal densities have exceeded those of hard drives since last year! Coughlin Associates provides several charts in the article which map lab demos and product HDD areal density since 2000, and contrasts that to new flash product announcements.  Coughlin comments that "Flash memory areal density exceeding HDD areal density is important since it means that flash memory products with higher capacity can be built using the same surface area." Check out the entire article here.

The debate between hard drives and solid state drives goes on in 2016, particularly in the area of areal densities – the actual density of storage on a device.  Fortunately for us, Tom Coughlin, SNIA Solid State Storage Initiative Education Chair, and a respected analyst who contributes to Forbes, has advised that flash memory areal densities have exceeded those of hard drives since last year!

Coughlin Associates provides several charts in the article which map lab demos and product HDD areal density since 2000, and contrasts that to new flash product announcements.  Coughlin comments that “Flash memory areal density exceeding HDD areal density is important since it means that flash memory products with higher capacity can be built using the same surface area.”

Check out the entire article here.