Lecture 17 - SSDs and Files

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Workloads

Disk Performance Metrics

Solid-State Storage (SSDs)

NAND Flash Cell Types

SSD Structure

Block/Page Layout

Striping

SSD Operation Latency

Flash Translation Layer (FTL)

FTL #1: Direct Mapping

FTL #2: Log-Based Mapping

Garbage Collection

Overprovisioning

SSDs vs. Hard Drives (Throughput)

SSD Summary

What is a File?

Inodes

File API (Attempt 1) — Inode Numbers

Paths and Directories

Directory Tree

Current Directory

Path Name Translation

Directory Calls

Special Directory Entries

File API (Attempt 2) — Paths

File Descriptors

FD Table in xv6

File API (Attempt 3) — File Descriptors

Multiple FDs to the Same File

lseek — Non-Sequential Reads

fork() and File Descriptors

fsync — Communicating Durability Requirements

Deleting Files

rename

Atomic File Update

Summary

Source