sdc 2015 - host managed smr · © 2013 western digital technologies, inc. all rights reserved. sdc...

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SDC 2015 - Host Managed SMR

Albert Chen • Jim Malina • TK Kato

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Shingled Magnetic Recording

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Track Pitch

Track Pitch

Random Write

Random Read Sequential Write

Random Read

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Abstraction Layers

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Storage Stack File system ApplicationFirmware Driver

© 2013 WESTERN DIGITAL TECHNOLOGIES, INC. ALL RIGHTS RESERVED. 6 http://hselin.com/blog/2015/08/26/another-layer-of-indirection

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For an in-depth presentation on how to handle host managed/aware SMR devices.

Wednesday 1:00 – 1:50

Strategies for Using Standard File systems on SMR Drives

Dr. Hannes Reinecke

SUSE

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SMR Type Drive Managed Host Managed

Method Handle random writes Sequential write

Usage scenario Client Data center/Surveillance/24x7

Pros Plug & play More efficient data mgmt

Cons Higher drive complexity

Unpredictable performance

SW support required Not backwards

compatible

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Faster drive development

Access to application & system level semantics

Predictable drive performance

Scale with host HW

Fewer Drive Resources

Easier to manage

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Zone Block Command

+ Zone ATA Command --------------------------------- Host Managed SMR

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WP

Partially filled SMR zoneWP

Partially filled SMR zone

Write

Write

Write

Write

Write

Read

Read

Read

Read

Fully filled SMR zone

Read

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SMR Device Mapper

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CMR Zone SMR Zone ... SMR ZoneSMR Zone SMR Zone

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Acts as media-cache outside the drive with more robust resources available from the host

Write Log: “Media cache” for random writes consists of SMR and CMR zone(s)

Write Buffer: Descriptor for allocated data in Write Log

Backstore: SMR zones that makes up advertised capacity (subsumes Write Buffers during GC)

Write BufferWrite

Buffer

SMR Write Log[0...Y-1]

Write Buffer

Backstore (advertised capacity)CMR Write Log[0...X-1]

...CMR Zone 0 CMR Zone X ...SMR Zone 0 SMR Zone Y ...SMR Zone Y + 1 SMR Zone Z

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SMR Write Log[0...Y-1] Backstore (advertised device capacity)CMR Write Log[0...X-1]

...CMR Zone 0 CMR Zone X ...SMR Zone 0 SMR Zone Y ...SMR Zone Y + 1 SMR Zone Z

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Thanks!

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One more thing…

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SMR Simulator

https://github.com/westerndigitalcorporation/SMR-Simulator

Last month, WD released a SMR simulator to facilitate host-side software/file system development. SMR-Simulator is a simple tool that captures host software behavior and determines its “friendliness” to SMR technology. We hope SMR-Simulator will enable open source developers to experiment and become familiar with SMR functionalities and behaviors without the need to access real SMR (ZBC/ZAC) HW.

http://hselin.github.io/blog/2015/08/23/host-managed-smr-simulator

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Contact us

Albert Chen Albert.Chen@wdc.com https://www.linkedin.com/in/alberthchen

Jim Malina Jim.Malina@wdc.com https://www.linkedin.com/in/jimmalina

Takeaki Kato TK.Kato@wdc.com https://www.linkedin.com/pub/takeaki-kato/6/436/78