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Advancing Storage Management with OHSM: A Linux Perspective

The Open Hierarchical Storage Manager (OHSM) project aims to optimize data storage on Linux, particularly in handling online data relocation between varying storage tiers. Initiated during university competitions, the project is spearheaded by a team from the University of Pune, guided by industry professionals. OHSM addresses the significant cost disparities between consumer-grade and high-end SSD storage by enabling enterprises to implement policy-based management for data placement and relocation. It leverages existing kernel functionalities while striving to integrate with mainline Linux.

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Advancing Storage Management with OHSM: A Linux Perspective

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  1. ONLINE HIERARCHICAL STORAGE MANAGER FOR LINUX Ottawa Linux Symposium 2009

  2. Who am I ? • Greg Freemyer • CTO and Litigation Triage Solutions Specialist at The Norcross Group • Using UNIX since 1983, and have an interest in storage systems • HP certified Master SAN Architect • Participate in several kernel mailing lists and try to help out on kernelnewbies • I did not write any of OHSM, but I became an advisor to the project after becoming aware of them via the kernelnewbies mailing list

  3. OHSM Team • The ohsm team was formed to compete in various university competitions • University of Pune, India • The team comprises of currently six members • Project Mentor- SandeepKumar Sinha, NetApp, India • Students - RishiBhushanAgrawal, RohitKumar Sharma, RohitVashist, SnehaHendre, VineetAgarwal • Competition results • Third Prize at Cognizance’ 09 held at Indian Institute of Technology, Roorkee. • Consolation prize at Techkriti’ 09 held at Indian Institute of Technology, Kanpur. • First Prize at INNOVATION 2k9 held at Cummins College of Engineering, Pune. • Second Prize at Jishin’ 09 held at BhartiVidyapeeth College of Engineering for Women, Pune. • Third Prize at Techno Dream’ 09 held at Maharashtra Academy of Engineering, Alandi.

  4. Why OHSM ? • Extremely large cost ratio between low-cost consumer grade storage to high-end SSD class storage • Bare SATA ~ $100/TB     Bare Intel SSD ~ $5,000/TB* • Enterprises need online relocation of data between storage tiers • Enterprise Application Security Audits make moving data from one logical location to another difficult and expensive • No open source solution * Based on $750 for a 160GB Intel SSD on July 9, 2009

  5. What is OHSM ?

  6. File System Scanner Relocation Policy TRIGGER Home= 1 Home = 3 Dest = 3 Dest = 0 Dest = 0 Tier 1 Tier 2 Tier 3

  7. OHSM Goals ? • Leveraging Hybrid aggregates (volumes) • Policy based initial placement of files • Online relocation of data between tiers • Leverage user space, existing ABIs, and existing kernel functionality • Minimal Patches to existing filesystem(s) • Kernel Module isolating OHSM kernel logic • Mainline kernel inclusion

  8. Complexity and Challenges • Relocating open files • Keeping file system online • Ranged block allocation • Getting device mapping from device mapper

  9. Status of project • Prototype implementation on ext2 with both kernel and user space code • Design documents and full source available for ext2 prototype available for download • ext3 testing in progress • ext4 is in the architectural discussion stage

  10. Prototype Architecture

  11. High Level Architecture

  12. Detailed Architecture

  13. User Space Components OHSM User Interface OHSM Administrator Device Topology Device Mapper Library XML Parser

  14. OHSM Kernel Driver

  15. File System

  16. Sample policy file in XML <DEVICES> <DEV_TIER_INFO> <NR_TIERS>3</NR_TIERS> <NR_DEVICES>6</NR_DEVICES> </DEV_TIER_INFO> <DEV_TIER> <TIER>1</TIER> <DEVICE>/dev/md4</DEVICE> <DEVICE>/dev/md5</DEVICE> <TIER>2</TIER> <DEVICE>/dev/md3</DEVICE> <TIER>3</TIER> <DEVICE>/dev/md1</DEVICE> <DEVICE>/dev/md2</DEVICE> <DEVICE>/dev/md6</DEVICE> </DEV_TIER> </DEVICES>

  17. Policy File Generator : Allocation

  18. Policy File Generator : Relocation

  19. Policy File Generator : Tier Device

  20. Configuration Files • /etc/ohsm/dtd_alloc.dtd • /etc/ohsm/dtd_reloc.dtd • /etc/ohsm/dtd_device.dtd • /etc/ohsm/ohsm.conf

  21. User space / Kernel APIs • Enable/Disable OHSM • ioctlservices • Set Allocation and Relocation Policies • Set Tier Device Mappings • Enable/Disable Relocation Policy ( Based on Relocation rule ID or Rule No) • Triggering relocation • Get Tier Status  (No. of allocated/free blocks)

  22. Ext4 implementation • New Architecture design for ext4 supporting per-inodepreallocation and per-CPU locality preallocation • Ted Tso's Dec. 8, 2008 ext4 post 1 - 3 new ioctls: • Blocks NOT to allocate from – global • Preferred Block range to Allocate from -  Inode specific • replace blocks with donor blocks - Inodespecific 1 - http://markmail.org/message/qp7zjhhdzxum7rfn

  23. Ext4 Implementation…. • Akira Fujita Patches • EXT4_IOC_ADD_GLOBAL_ALLOC_RULE 2– rfc • EXT4_IOC_ADD_INODE_ALLOC_RULE 2– rfc • EXT4_IOC_MOVE_EXT 3- in 2.6.31-rc series • Open/Create Hooks • Home and Destination Tier, where to store? 2 - http://markmail.org/message/yigzopzx2gkdjyw3 3 - http://markmail.org/message/a43cgtefhhz45slc

  24. What is the OHSM Project ? • Effort to build platform for HSM on Linux • Idea came when thinking of hybrid aggregates (SSD + Rotational) • Its hosted at code.google.com/p/fscops and ohsm.sourceforge.net • Open to all

  25. Future of OHSM ? • A free Open Source Hierarchical Storage Manager for Linux framework • Ext4 support • Submission of patches to mainline • Allocation based on directories • Analytical Engine to trigger relocation • Support for extending FS when Logical Volume is extended • Allocating inodes from optimum tier based on policy

  26. ? Questions

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