Presentation on theme: "Better I/O Through Byte-Addressable, Persistent Memory"— Presentation transcript:
1 Better I/O Through Byte-Addressable, Persistent Memory Jeremy Condit, Ed Nightingale, Chris Frost,Engin Ipek, Ben Lee, Doug Burger, Derrick Coetzee
2 A New World of Storage DRAM + Fast + Byte-addressable - Volatile Disk / Flash+ Non-volatile- Slow- Block-addressable
3 A New World of Storage BPRAM + Fast + Byte-addressable + Non-volatile Byte-addressable, Persistent RAMBPRAM+ Fast+ Byte-addressable+ Non-volatileHow do we build fast, reliable systems with BPRAM?
4 Phase Change Memory Most promising form of BPRAM “Melting memory chips in mass production” – Nature, 9/25/09
5 Phase Change Memory phase change material (chalcogenide) Properties slow cooling -> crystalline state (1)phase change material(chalcogenide)fast cooling -> amorphous state (0)PropertiesReads: 2-4x DRAMWrites: 5-10x DRAMEndurance: 108+electrode
6 A New World of Storage BPRAM + Fast + Byte-addressable + Non-volatile Byte-addressable, Persistent RAMBPRAM+ Fast+ Byte-addressable+ Non-volatileHow do we build fast, reliable systems with BPRAM?Disk / Flash+ Non-volatile- Slow- Block-addressableThis talk: BPFS, a file system for BPRAMResult: Improved performance and reliability
7 Goal New guarantees for applications File system operations will commit atomically and in program orderYour data is durable as soon as the cache is flushedNew mechanism: short-circuit shadow paging
8 Design Principles1. Eliminate the DRAM buffer cache; use the L1/L2 cache instead2. Put BPRAM on the memory bus3. Provide atomicity and ordering in hardwareWrite AWrite B
10 BPRAM in the PC BPRAM and DRAM are addressable by the CPU Physical address space is partitionedBPRAM data may be cached in L1/L2L1L2Memory busDRAMBPRAMHD / FlashPCI/IDE bus
11 BPFS: A BPRAM File System Guarantees that all file operations execute atomically and in program orderDespite guarantees, significant performance improvements over NTFS on the same mediaShort-circuit shadow paging often allows atomic, in-place updates
12 BPFS: A BPRAM File System root pointerindirect blocksinodefileinodesfiledirectoryfile
13 Enforcing FS Consistency Guarantees What happens if we crash during an update?Disk: Use journaling or shadow pagingBPRAM: Use short-circuit shadow paging
14 Review 1: Journaling Write to journal, then write to file system BB’journalA’B’Reliable, but all data is written twice
15 Review 2: Shadow Paging Use copy-on-write up to root of file system file’s root pointerABA’B’Any change requires bubbling to the FS rootSmall writes require large copying overhead
16 Short-Circuit Shadow Paging Inspired by shadow pagingOptimization: In-place update when possible
17 Short-Circuit Shadow Paging Inspired by shadow pagingOptimization: In-place update when possiblefile’s root pointerABA’B’Uses byte-addressability and atomic 64b writes
18 Opt. 1: In-Place Writes Aligned 64-bit writes are performed in place Data and metadatafile’s root pointerin-place write
20 BPFS Example Cross-directory rename bubbles to common ancestor inode root pointeradd entryremove entryindirect blocksinodefileinodesdirectorydirectoryfileCross-directory rename bubbles to common ancestor
24 Enforcing Ordering and Atomicity Solution: Epoch barriers to declare constraintsFaster than write-throughImportant hardware primitive (cf. SCSI TCQ)AtomicitySolution: Capacitor on DIMMSimple and cheap!
25 Ordering and Atomicity Ineligible for eviction!L1 / L22...CoWBarrierCommit1BPRAMMP works too(see paper)
27 Methodology Built and evaluated BPFS in Windows Three parts: Experimental: BPFS vs. NTFS on DRAMSimulation: Epoch barrier evaluationAnalytical: BPFS on PCM
28 Microbenchmarks NTFS - Disk NTFS - RAM BPFS - RAM NOT DURABLE!
29 BPFS Throughput On PCM BPFS - PCM Projected Throughput NTFS Disk NTFS RAMBPFSRAMBPFSPCM(Proj)Sustained Throughput of PCM (MB/s)
30 Conclusions BPRAM changes the trade-offs for storage Use consistency technique designed for mediumShort-circuit shadow paging:improves performanceimproves reliabilityBonus: PCM chips on display at poster session!
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