Computer Science 440 Spring 2014
Gregory M. Kapfhammer
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Operating Systems
File Systems
Why?
Store and Retrieve
Did not exist?
Examples?
Characteristics?
Size
Persistence
Sharing
Magnetic Disks
SSDs
Read block k
Write block k
Find?
Protect?
Free?
Concrete example: permissions
ls -alg
chmod
Files
Persistent
File system
Files as an abstraction mechanism
File naming
Special characters?
Capitalization?
Unix
MS-DOS
Two part file names
Purpose?
Unix
Convention
Human readable
.htm vs .html
Difference?
.tex
Connect to Programs
Types of File
Regular
Directory
Special
ASCII
Unicode
Text
Binary
vim usesizeof
strings usesizeof
Meaning?
Sequential files
Random-access files
Database?
Attributes
Metadata
Page 263
File operations
Page 265
Directories
Hierarchy
Absolute path
Relative path
Working directory
Directory operations
Page 272
Hard link
Soft link
Cycles
Let's try it!
ln -s
MBR
Partitions
/etc/fstab
Meaning?
"sd" used to mean "SCSI device"
Partition number
Boot block
Superblock
File implementation
Allocation?
Contiguous
How does it work?
Page 275
Problems?
Disk fragmentation
Feasibility of compaction?
Hole filing?
Alternatives?
FAT
Page 278
Does not scale to large disks!
inodes
Per-file index
Find blocks of the file
Unix
Directories
Linear Searching
Hashing
Shared Files
DAG
Symbolic Links
Hard links
Compare and contrast?
"Robustness in the face of failure"
LFS
JFS
Idempotency
Additional Topics
Disk Quotas
Disk Backups
Cache
Defragmentation
sshfs
Cloud Storage