Storage Class MemoryPresented by Charith Suriyakula (168269B)

Content

Introduction of Storage Class Memory (SCM)

Key features of SCM

Candidate device technologies

Comparison

Concerns

Future of SCM

Conclusion

Introduction

Storage Memory

Hard disk

External devices (CD, DVD, USB drive, etc.)

Memory is typically with high performance and low capacity

HDD is typically high capacity, affordable but low performance

What is Storage Class Memory (SCM)

It is a non-volatile storage medium

It has capacity and economics similar to HDD / SSD and with performance that’s similar to memory / RAM

How SCM works

How SCM works SCM is created out of flash-based

NAND To build a SCM, combine scalable

non-volatile memory with ultra high density integration

Using micro to nano addressing Using multi-level cells Using 3D stacking

Key features

Low latency – High speed read / write Low Cost Persistent / Non-volatile

Key features

SCM is based on several key technologies Direct Access Storage (DAS) Byte Accessible Storage (BAS) Persistent Memory (PM) Non-Volatile Memory (NVM)

New driver model SCM Bus driver

SCM Bus driver enumerates the physical and logical SCM devices in the system SCM Disk driver

This acts as a storage abstraction layer to the rest of the OS

Candidate device technologies

Improving FLASH Flash memory is a type of EEPROM (Electronically

Erasable Programmable Read Only Memory) chip Improvements in latency and speed

Candidate device technologies

Magnetoresistive RAM – MRAM Data stored by magnetic storage elements Difficult to scale, capacity limitations and high cost Spin-Transfer Torque MRAM

Candidate device technologies

Ferroelectric RAM - FeRAM This has Ferro-electric layer to achieve non-volatility Low power usage, fast writing performance Low storage density compared wo flash Difficult to scale, capacity limitations and high cost

Candidate device technologies

RRAM / ReRAM – Resistive RAM Works by changing the resistance across di-

electric solid state material Storage density is high - storage chips that

will be able to pack in a terabyte worth of data in a tiny space

Low energy consumption More storage manufacturers rely on ReRAM

to develop SCM in future

Candidate device technologies

Phase change memory – PCM This uses the unique characteristics of Chalcogenide glass Glass is converted into it’s crystalline state by quickly heat and quench the glass Much higher performance Have to consider the PCM’s temperature senility

Comparison

Concerns

Existing interface may not support the new developments in SCM – vendors have to adapt to the technology

Traditional storage protocols (SATA / SAS) may be bottleneck to achieve the full performance from SCM modules

File system compatibility issues Garbage collection will perform only in the flash that it is assigned to, resulting of

unused flash cells inaccessible for other controllers Multi-controller environment requires multi-threaded applications Flash management intelligence require additional changes in PCIe board as well as

flash drivers

Future of SCM

High capacity mobile devices

SSD with ReRAM technology – much higher performance and capacity

Conclusion

To meet the increasing demand in servers, power and space will be a key consideration

To support that, HDD and Storage Flash will no suffice SCM provides

High performance and robustness of a Solid State Memory Capacity and economical aspects of HDD

References

1. George Crump, What Is Storage Class Memory?, http://www.storage-switzerland.com/Articles/Entries/2011/12/13_What_Is_Storage_Class_Memory.html

2. Scott Davis, The next generation of storage disruption: storage-class memory, http://www.networkworld.com/article/3026720/storage/the-next-generation-of-storage-disruption-storage-class-memory.html

3. Geoffrey W. Burr, Storage Class Memory, IBM Research April 12,20104. Robin Harris, The non-volatile memory revolution: Bigger than SSDs,

http://www.zdnet.com/article/the-non-volatile-memory-revolution/ 5. Neal Christiansen, Storage Class Memory support in Windows OS, Storage Developer Conference 20156. G. W. Burr, et al, Overview of candidate device technologies for storage-class memory (2008), IBM Journal

of Research and Development7. Janusz J Nowak, et al, Dependence of Voltage and Size on Write Error Rates in Spin-Transfer Torque

Magnetic Random-Access Memory, IEEE Magnetics Letters (Volume:7 )