Analysis and Evolution of Journaling File Systems By: Vijayan Prabhakaran, Andrea and Remzi Arpai-Dusseau Presented by: Andrew Quinn EECS 582 – W161

Outline File System Background Description of novel tools Analysis of Ext3 EECS 582 – W162

Background of File Systems EECS 582 – W163 Unix File System Fast File System Journaling File System Improve Performance Fast Crash Recovery

Journaling File System EECS 582 – W164 Journaling File System JournalFixed-block FS Write “hello world” to file 1. Meta-data for file 2. Write “hello world” Client 3. Write commit

Journaling FS What should we write to the journal? Meta-data? Actual data? When should we `commit’ data to the journal? After each journal entry? After the data is written to the disk? EECS 582 – W165

Journaling modes (ext3) EECS 582 – W166

Contributions Semantic Block Analysis (SBA) Semantic Trace Playback (STP) An analysis of journaling file systems using SBA An evaluation of design changes to ext3 using SBA EECS 582 – W167

Traditional FS analysis EECS 582 – W168 SystemProgrammer Synthetic/real workload Full system performance

SBA analysis EECS 582 – W169 SBAProgrammer Targeted synthetic workload Block-level tracing Semantic info

SBA analysis EECS 582 – W1610 Block-level analysis: Block number – understand seq. or random access Timing of each block - understand bursts of traffic Semantic information: Distinguish between journal blocks and in-place data

SBA Implementation Implemented as a pseudo-device driver Slight customizations for each File system EECS 582 – W1611

STP EECS 582 – W1612 STP Block level trace High level FS ops Performance estimate

Ext3 `Basic Behavior’ EECS 582 – W1613

Ex3 and Concurrency EECS 582 – W1614

Ex3 in Ordered mode EECS 582 – W1615

Ext3 and STP Evaluate changes to key characteristics: Journal location Transaction grouping Timing Adaptive journaling Journal contents EECS 582 – W1616

Journal Location EECS 582 – W1617

Untangling Transaction Groups EECS 582 – W1618

Timings EECS 582 – W1619

Ext3 and STP Adaptive Journaling Mode Ordered: Data: Adaptive Journaling contents Write data block differences into journal Size reduction by factor of 200 for TPC-B Size reduction by factor of 6 for TPC-C EECS 582 – W1620

Conclusion We can leverage SBA to understand the semantic behavior of a journaling FS We can leverage STP to predict the effect of algorithmic changes to a journaling FS EECS 582 – W1621