File System Flashcards
Types of Data?
Numeric
Character
Binary
File Attributes?
Name Identifier Type Location Size Protection Time, date
File Operations?
Create Write Read Reposition - Seek Delete Truncate Open Close
Open Files?
Open-file table: tracks open files.
File Pointer: Pointer to last read/write location, per process that has the file open.
File-open count: counter of number of times a file is open, to allow removal of data from open-file table.
Open File Locking?
Similar to reader-writer locks
Shared lock similar to reader lock - several processes can acquire concurrently.
Exclusive lock similar to writer lock
Mandatory?
Access is denied depending on locks held and requested
Advisory?
Processes can find status of locks and decide what to do
File Structure?
None
Simple Record Structure
Compex Structures
Access Methods?
Sequential Access
Direct Access
Sequential Access
Read next
Write next
reset
Direct Access?
File is fixed length logical records. Read n write n position to n --read next --write next rewrite n
Disk structure?
Disk can be subdivided into partitions
Disk can be RAID protected against failure
Operations Performed on Directory?
Search for a file Create a file Delete a file List a directory Rename a file Traverse a file system
The directory is organized logically to obtain?
Efficiency
Naming
Grouping
Acyclic-Graph Directories
Two different names
If dict deletes list -> dangling pointer.
Solution to dangling pointer?
Backpointers, so we can delete all pointers variable size records a problem.
Backpointers using a daisy chain organization
Entry-hold-count solution
New directory entry types?
Link - another name
Resolve the link - follow pointer to locate the file
File Sharing?
Sharing of files on multi-user systems is desirable
Sharing may be done through a protection scheme
If multi-user system?
User IDs identify users, allowing permissions and protections to be per-user.
Group IDs allow users to be in groups, permitting group acscess rights
Types of File Sharing?
Manually via FTP
Automatically via DFS
Semi-Automatically via WWW
Client-Server?
Model allows clients to mount remote file systems from servers.
Server can serve multiple clients
Client and user-on-client identification is insecure or complicated.
Client-Server types?
NFS
CIFS
NFS?
Is standard UNIX client-server file sharing protocol
CIFS?
is standard windows protocol
