Versioning File System Shengan Zheng, Linpeng Huang, Hao Liu, Linzhu - - PowerPoint PPT Presentation

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Versioning File System Shengan Zheng, Linpeng Huang, Hao Liu, Linzhu - - PowerPoint PPT Presentation

Jan 29, 2023 183 likes •456 views

HMVFS: A Hybrid Memory Versioning File System Shengan Zheng, Linpeng Huang, Hao Liu, Linzhu Wu, Jin Zha Department of Computer Science and Engineering Shanghai Jiao Tong University Outline Introduction Design Implementation

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SLIDE 1

HMVFS: A Hybrid Memory Versioning File System

Shengan Zheng, Linpeng Huang, Hao Liu, Linzhu Wu, Jin Zha

Department of Computer Science and Engineering Shanghai Jiao Tong University

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SLIDE 2

Outline

  • Introduction
  • Design
  • Implementation
  • Evaluation
  • Conclusion
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SLIDE 3

Introduction

  • Emerging Non-Volatile Memory (NVM)
  • Persistency as disk
  • Byte addressability as DRAM
  • Current file systems for NVM
  • PMFS, SCMFS, BPFS
  • Non-versioning, unable to recover old data
  • Hardware and software errors
  • Large dataset and long execution time
  • Fault tolerance mechanism is needed
  • Current versioning file systems
  • BTRFS, NILFS2
  • Not optimized for NVM
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SLIDE 4

Design Goals

  • Strong consistency
  • A Stratified File System Tree (SFST) represents the snapshot of whole file system
  • Atomic snapshotting is ensured
  • Fast recovery
  • Almost no redo or undo overhead in recovery
  • High performance
  • Utilize the byte-addressability of NVM to update the tree metadata at the granularity of bytes
  • Log-structured updates to files balance the endurance of NVM
  • Avoid write amplification
  • User friendly
  • Snapshots are created automatically and transparently
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SLIDE 5

Overview

  • HMVFS is an NVM-friendly log-structured versioning file system
  • Space-efficient file system snapshotting
  • HMVFS decouples tree metadata from tree data
  • High performance and consistency guarantee
  • POSIX compliant
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SLIDE 6

Outline

  • Introduction
  • Design
  • Implementation
  • Evaluation
  • Conclusion
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SLIDE 7

On-Memory Layout

  • DRAM: cache and journal
  • Sequential write zone
  • File metadata and data
  • Tree data
  • Random write zone
  • File system metadata
  • Tree metadata
  • NVM:

Block Information Table (BIT) Node Address Tree Cache (NAT Cache ) Segment Information Table (SIT)

Random Writes Sequential Writes

NVM

Segment Information Table Journal

DRAM

Checkpoint Information Tree (CIT) Node Address Tree (NAT)

Main Area (SFST) Auxiliary Information

Node Blocks Checkpoint Blocks (CP) Data Blocks Superblock Superblock

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SLIDE 8

in traditional Log-structured File Systems

  • Update propagation problem

Direct pointer Or Inline data Metadata Single-indirect Double-indirect Triple-indirect Inode block Direct node Direct node Indirect node Indirect node Indirect node Direct node Direct node Data block Direct node Indirect node

Data Node

… … … … … … … … … … … Data block Data block Data block Data block Data block Data block Data block Data block Indirect node Inode

Updated blocks

Direct node Data block

Index Structure

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SLIDE 9

Index Structure without write amplification

  • Node Address Table

Direct pointer Or Inline data Metadata Single-indirect Double-indirect Triple-indirect Inode block Direct node Direct node Indirect node Indirect node Indirect node Direct node Direct node Data block Direct node Indirect node

Data Node

… … … … … … … … … … … Data block Data block Data block Data block Data block Data block Data block Data block

Updated blocks

Direct node Data block

Node Address Table

Node-ID Address … … n-1 0x38 n 0x42 n+1 0x24 … … 0x73

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SLIDE 10

Index Structure for versioning

  • Node Address Table with the dimension of version.

Direct pointer Or Inline data Metadata Single-indirect Double-indirect Triple-indirect Inode block Direct node Direct node Indirect node Indirect node Indirect node Direct node Direct node Data block Direct node Indirect node

Data Node

… … … … … … … … … … … Data block Data block Data block Data block Data block Data block Data block Data block

Updated blocks

Direct node Data block

Node Address Table with Version

Node-ID Address … … n-1 0x14 n n+1 0x24 … … 0x42 Address … 0x38 0x24 … x42 Address … 0x38 0x24 … 0x73

Version1 Version2 Version3

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SLIDE 11

How to store different trees space-efficiently

  • Node Address Tree (NAT)
  • A four-level B-tree to store multi-version Node Address

Table space-efficiently

  • Adopt the idea of CoW friendly B-tree
  • NAT leaves contain NodeID-address pairs
  • Other tree blocks in NAT contain pointers to lower level

blocks.

Node NAT root NAT internal NAT internal NAT leaf NAT leaf NAT leaf Indirect node NAT internal NAT internal NAT internal NAT root NAT internal NAT internal NAT leaf Direct node Inode Direct node Node Address Tree

P,1 A,1 B,1 C,1 D,1 E,1 F,1 P,1 A,1 B,1 C,2 D,1 E,2 F,1 Q,1 D',1 F',1 P,0 A,1 B,1 C,1 D,0 E,1 F,0 Q,1 D',1 F',1 Original New

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SLIDE 12

Stratified File System Tree (SFST)

  • Four different categories of blocks:
  • Checkpoint layer
  • Node Address Tree (NAT) layer
  • Node layer
  • Data layer
  • All blocks from SFST are stored in the main area with

log-structured writes

  • Balance the endurance of NVM media
  • Each SFST represents a valid snapshot of file system
  • Share overlapped blocks to achieve space-efficiency

Data block Data block Data block Data block Data block Data block Node Data NAT root NAT internal NAT internal NAT leaf NAT leaf NAT leaf Indirect node NAT internal NAT internal NAT internal NAT root NAT internal NAT internal NAT leaf Direct node Inode Direct node Node Address Tree Original snapshot New snapshot CP block CP block Checkpoint

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SLIDE 13

Stratified File System Tree (SFST)

  • The metadata of SFST
  • In auxiliary information zone
  • Random write updates
  • Segment Information Table (SIT)
  • Contains the status information of every segment
  • Block Information Table (BIT)
  • Keeps the information of every block
  • Update precisely at variable bytes granularity
  • Contains:
  • Start and end version number
  • Block type
  • Node ID
  • Reference count

Data block Data block Data block Data block Data block Data block Node Data NAT root NAT internal NAT internal NAT leaf NAT leaf NAT leaf Indirect node NAT internal NAT internal NAT internal NAT root NAT internal NAT internal NAT leaf Direct node Inode Direct node Node Address Tree Original snapshot New snapshot CP block CP block Checkpoint

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SLIDE 14

Garbage Collection in HMVFS

  • Move all the valid blocks in the victim segment to the current segment
  • When finished, update SIT and create a snapshot
  • Handle block sharing problem

NAT block Node Block 1 Node Block 2

Version 1

NAT block Node Block 2

Version 2

NAT block Node Block 2

Version 3

NAT block Node Block 2

Version 4 Segment A Segment B

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SLIDE 15

Outline

  • Introduction
  • Design
  • Implementation
  • Evaluation
  • Conclusion
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SLIDE 16

Block Information Table (BIT)

  • Block sharing problem
  • The corresponding pointer in the parent block must be updated if a new child block is

written in the main area

  • Node ID and block type
  • Used to locate parent node

Type of the block Type of the parent Node ID Checkpoint N/A N/A NAT internal NAT internal Index code in NAT NAT leaf Inode NAT leaf Node ID Indirect Direct Data Inode or direct Node ID of parent node

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SLIDE 17

Block Information Table (BIT)

  • Start and end version number
  • The first and last versions in which the block is valid
  • Operations like write and delete set these two variables to the current version

number

  • Reference count
  • The number of parent nodes which are linked to the block
  • Update with lazy reference counting
  • File level operations and snapshot level operations update the reference

count

  • If the count reaches zero, the block will become garbage
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SLIDE 18

Snapshot Creation

  • Strong consistency is guaranteed
  • Flush dirty NAT entries from DRAM to form a new

Node Address Tree

  • Follow the bottom-up procedure
  • Status information are stored in checkpoint block
  • Space-efficient snapshot
  • The atomicity of snapshot creation is ensured
  • Atomic update to the pointer in superblock to announce

the validity of the new snapshot

  • Crash during snapshot creation can be recovered by

undo or redo depend on the validity

Node Data NAT root NAT internal NAT internal NAT leaf NAT leaf NAT leaf Indirect node NAT internal NAT internal NAT internal NAT root NAT internal NAT internal NAT leaf Direct node Inode Direct node Node Address Tree Original snapshot New snapshot CP block CP block Checkpoint

Data block Data block Data block Data block Data block Data block … … … … … … …

Super Block

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SLIDE 19

Snapshot Deletion

  • Deletion starts from the checkpoint block
  • Checkpoint cache is stored in DRAM
  • Follows the top-down procedure to decrease reference counts
  • Consistency is ensured by journaling
  • Call garbage collection afterwards
  • Many reference counts have decreased to zero

P,0 A,1 B,1 C,1 D,0 E,1 F,0 Q,1 D',1 F',1 P,1 A,1 B,1 C,2 D,1 E,2 F,1 Q,1 D',1 F',1

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SLIDE 20

Crash Recovery

  • Mount the writable last completed snapshot
  • No additional recovery overhead
  • Mount the read-only old snapshots
  • Locate the checkpoint block of the snapshot
  • Retrieve files via SFST

Checkpoint Checkpoint Checkpoint Checkpoint Superblock NAT root … NAT root … NAT root … NAT root …

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SLIDE 21

Outline

  • Introduction
  • Design
  • Implementation
  • Evaluation
  • Conclusion
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SLIDE 22

Evaluation

  • Experimental Setup
  • A commodity server with 64 Intel Xeon 2GHz processors and 512GB DRAM
  • Performance comparison with PMFS, EXT4, BTRFS, NILFS2
  • Postmark results
  • Different read bias numbers

20 40 60 80 100 120 140 160 180 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

sec Percentage of Reads

HMVFS BTRFS NILFS2 EXT4 PMFS

20 40 60 80 100 120 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Efficiency (sec-1) Percentage of Reads

HMVFS BTRFS NILFS2

Transaction performance Snapshotting efficiency

2.7x and 2.3x

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SLIDE 23

Evaluation

  • Filebench results
  • Fileserver
  • Different numbers of files

5 10 15 20 25 2k 4k 8k 16k

  • ps/sec (x1000)

Number of Files HMVFS BTRFS NILFS2 EXT4 PMFS 5 10 15 20 25 30 35 40 2k 4k 8k 16k Efficiency (sec-1) Number of Files HMVFS BTRFS NILFS2

Throughput performance Snapshotting efficiency

9.7x and 6.6x

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SLIDE 24

Evaluation

  • Filebench results
  • Varmail
  • Different depths of directories

2 4 6 8 10 12 0.7 1.2 1.4 2.1 Efficiency (sec-1) Directory Depth HMVFS BTRFS NILFS2 5 10 15 20 25 0.7 1.2 1.4 2.1

  • ps/sec (x1000)

Directory Depth HMVFS BTRFS NILFS2 EXT4 PMFS

Throughput performance Snapshotting efficiency

8.7x and 2.5x

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SLIDE 25

Outline

  • Introduction
  • Design
  • Implementation
  • Evaluation
  • Conclusion
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SLIDE 26

Conclusion

  • HMVFS is the first file system to solve the consistency problem for NVM-based

in-memory file systems using snapshotting.

  • Metadata of the Stratified File System Tree (SFST) is decoupled from data and is

updated at byte granularity

  • HMVFS stores the snapshots space-efficiently with shared blocks in SFST and

handles write amplification problem and block sharing problem well

  • HMVFS exploits the structural benefit of CoW friendly B-tree and the byte-

addressability of NVM to automatically take frequent snapshots

  • HMVFS outperforms tradition versioning file systems in snapshotting and

performance while providing strong consistency guarantee and having little impact on foreground operations

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SLIDE 27
  • Q & A
  • Thank you