DDR4 NVDIMM Standardization: DDR4 NVDIMM Standardization: DDR4 NVDIMM Standardization: DDR4 NVDIMM Standardization: Now and FutureNow and Future

Server Forum 2014 Copyright © 2014 Micron Technology, Inc

NVDIMM DefinitionNVDIMM Definition

• One of several Hybrid DIMM versions

• RDIMM/LRDIMM-like DRAM module with storage memory components, controller and bus isolation

• Plugs into a standard DIMM socket

• No direct access to on-module storage memory (NAND)– Only used for DRAM backup/restore (limited by protocol &

controller)

• On-module storage memory provides persistence in event of power fail

• Backup power source required– Tethered ultracap or back-up power through 12V pins

NonNon--Volatile DIMM (NVDIMM)Volatile DIMM (NVDIMM)Persistent Memory Enabled by DRAM + NANDPersistent Memory Enabled by DRAM + NAND

• HW Architecture– RDIMM with bus isolation,

storage memory, and controller

• FW Architecture– Save on Power loss– Restore on Reboot– “SAVE” operation through

I2C command or “SAVE” HW signal

UltraCap ModuleSelf-contained energy source

for operation during power failure

Onboard DRAM & NANDDRAM performance

Oil & Gas

ExplorationMedical

ResearchFinancial

TransactionsPower Loss

Events

Big Data

AnalyticsFinancial Data

Integrity

HW signal

• Power-fail backup source– Typically 1:1 requirement

to NVDIMM– Tethered ultracap pack– 12V DIMM connector

DRAM performance

with data persistence

Integrated ControllerNAND management

and high speed DMA

MuxBus Isolation for

backup and restore

12VEnergy source,

DIMM connector

The Case for NVDIMMThe Case for NVDIMM

Picoseconds Nanoseconds Microseconds Milliseconds Seconds

CPU

Cache

SATA

SSD

SAS

SSDHDD

Significant hierarchy gap exists in current scale-out architectures

DRAM

PCIe

SSD

Performance

Persistence

Endurance

• Speed/performance driving large data sets to be stored in “warm” or “hot” locations (NVDIMM, PCI SSDs, etc.)

• NVDIMM used as storage cache acceleration in many instances

• Enterprise applications using real-time processing to capture, analyze, and respond intelligently to changing events

• Reliability/uptime is critical for enterprise IT resources

• Gaining momentum in several application spaces

Maintaining QoS while supporting increasingly demanding enterprise workloads are driving need for higher memory performance and density.

DDR4 12V Power Pins (1, 145) DDR4 12V Power Pins (1, 145) StandardizedStandardized

• Provides NVDIMM power for two possible situations• Tethered ultracap charging• Central back-up power using 12V pins during power loss

• Energy provided only for NVDIMM “SAVE” operation

• Ultracap charging• Charging will be significantly faster than 1.2V source• Charging will be significantly faster than 1.2V source

• Central back-up power• Eliminates need for individual ultracaps

• Allows for higher number NVDIMM/system• Allows for higher density NVDIMMs

• System required to handle status monitoring and health of backup power • Mechanism to get this information to NVDIMM

controller

DDR4 12V Power Pin DetailsDDR4 12V Power Pin DetailsPossible Future ConsiderationPossible Future Consideration

• Central back-up power scenario

• More definition/standardization required

• Minimum voltage specification• Amount of energy available• Amount of energy available• Length of up time after system power loss

• Back-up power health and status monitoring details

• System needs details to determine:

• Capability of backup source• Number and size of NVDIMMs the system can

support

DDR4 DDR4 SAVE_nSAVE_n Pin (230) Pin (230) StandardizedStandardized

• Similar to DDR3 HW signal used today to initiate NVDIMM backup

• Similar DDR3 system requirements prior to activating “SAVE_n” signal

• DRAM must be placed in self-refresh

• NVDIMM must be ready to perform a backup• Sufficient space in storage memory• Sufficient backup power

• Use of “SAVE_n” is the quickest way to initiate a backup

Operation Complete HW SignalOperation Complete HW SignalPossible Future ConsiderationPossible Future Consideration

• Current notice of completed backup or restore• Polling NVDIMM status registers

• Polling status reduces operational performance

• Standardizing an operation complete HW signal• Could be used for multiple operations

• Initialization• Initialization• Save• Restore

• Possible alternatives• Bidirectional signal (SAVE_n)• Separate pin multiplexed with other events such as (ALERT_n or

Event)

• Higher system performance than polling• Only interrupt CPU when operation complete• Less time spend in servicing operation

NVDIMM FWNVDIMM FWPossible Future Consideration Possible Future Consideration

• NVDIMM FW Control• Initialization• Backup• Restore• Status• Errors

Application3rd Party SW

Proprietary SW

SW Stack

BIOS/UEFI

OS• Errors• Ultracap Management• Storage Memory

Management

• Standardized FW features• Not necessarily a

standard FW interface• Simplifies MRC, BIOS,

and OS/Driver support

MRC

Driver

NVDIMM FW

RecognitionConfiguration

Initialization

Operational ControlFeatures Memory table

Application Interface

HW Control

Status

SummarySummary

• NVDIMM fulfills a need in the storage hierarchy

• Standardization opens up new growth opportunities

• Current 12V standard allows for efficient ultracap charging and a central backup power sourceand a central backup power source

• SAVE_n standard sets a efficient interface to signal a backup

• More standardization is possible in several areas

• Standardization drives wider adoption

• As more applications discover the benefits of NVDIMM new areas of standardization will probably follow