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Storage Class MemoryPresented by Charith Suriyakula (168269B)
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Content
Introduction of Storage Class Memory (SCM)
Key features of SCM
Candidate device technologies
Comparison
Concerns
Future of SCM
Conclusion
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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
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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
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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
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Key features
Low latency – High speed read / write Low Cost Persistent / Non-volatile
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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
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Candidate device technologies
Improving FLASH Flash memory is a type of EEPROM (Electronically
Erasable Programmable Read Only Memory) chip Improvements in latency and speed
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Candidate device technologies
Magnetoresistive RAM – MRAM Data stored by magnetic storage elements Difficult to scale, capacity limitations and high cost Spin-Transfer Torque MRAM
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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
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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
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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
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Comparison
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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
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Future of SCM
High capacity mobile devices
SSD with ReRAM technology – much higher performance and capacity
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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
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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 )