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ONLINE HIERARCHICAL STORAGE MANAGER FOR LINUX. Ottawa Linux Symposium 2009. 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
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ONLINE HIERARCHICAL STORAGE MANAGER FOR LINUX Ottawa Linux Symposium 2009
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
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.
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
File System Scanner Relocation Policy TRIGGER Home= 1 Home = 3 Dest = 3 Dest = 0 Dest = 0 Tier 1 Tier 2 Tier 3
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
Complexity and Challenges • Relocating open files • Keeping file system online • Ranged block allocation • Getting device mapping from device mapper
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
User Space Components OHSM User Interface OHSM Administrator Device Topology Device Mapper Library XML Parser
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>
Configuration Files • /etc/ohsm/dtd_alloc.dtd • /etc/ohsm/dtd_reloc.dtd • /etc/ohsm/dtd_device.dtd • /etc/ohsm/ohsm.conf
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)
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
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
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
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
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