Download Unix hardware level

UNIX & Windows NT
Name: Jing Bai
ID: 90297
Date:8/28/00
Content
1. Introduction
2. Kernel Architecture
3. File System
4. Memory Management
5. Security
6. Conclusion
Introduction
UNIX:
•It is a machine independent operating system. Ken Thompson developed it in 1969
• Unix OS was written by programmer to programmer. It use C language to instead of the
previously used assembly language
•Time-sharing, multi-user, multi-tasking are basic designed in the system(Multiple users can have
multiple tasks running at same time)
Windows NT
• Microsoft released it in 1993. It was a full 32-bit OS
• Its design goals include extensibility, portability, reliability, compatibility, performance and
international support.
Unix Kernel model
Unix
shell
User
program
u
s
Unix command program
library
library
Use
level
Kernel level
System call
interface
Process management subsystem
inter-process communication
process scheduling
File subsystem
Memory management
Disk block
cache
Int process 1
Character I/O
Swapper
process 0
Block I/O
Derive drivers
Hardware control-interrupt service
Figure 1
=Process
Hardware
Kernel level
Hardware level
Windows NT kernel mode
Logon
process
O/S
application
Win 16
application
Security
subsystem
O/S
system
Win 16
VDM
Win 32
application
MSDOD
application
POSIX
application
MSDOS
VDM
POSIX
system
Authentication
package
Win 32
subsystem
Security-accountmanage database
Executive
I/O manager
File system
cache manager
Device
drivers
User mode
Object
manager
Process
Securityreferencemonitor
manager
network
Virtualmemorymanager
Local
procedure call
facility
Kernel
drive
Hardware abstraction Layer
Kernel
Hardware
Figure 2
mode
UNIX File System
• UNIX file is a Hierarchical file structure. All the files are organized
into a multi-leveled hierarchy called a directory tree
•The file system supports two main objects: file and directory
• The directory contains a root directory with many subdirectories
• File is stored as an array of fixed-size data blocks with perhaps a
fragment
• The block sizes are set during a file system creation
UNIX File System Interface
The root directory
/
Directory files at
interior node
A
AA
B
dev
Other directories
and file
AB
d1
a1
a2
a3
Normal files at the leaves
f1
d2
Special files in the device directory/dev
UNIX File System Implementation
• IN Unix system, a file is represented by an Inode (Index Node)
• An Inode is a record that stores most of the information about a file
on the disk, such as its size and location. Each file has an own indoe,
all inodes have the same size
• The inode contains pointer that points to file block. In Unix, the first
12 pointers of inode point to blocks directly, so small files can be
accessed efficiently.
• Example for READ file
UNIX mapping of a file descriptor to an Inode
Data
blocks
Read(4...)





Tables of
open files
User space
Filestructure
table
System space
In-core
inode list
Inode
list
Disk space
UNIX Memory Management
• UNIX system uses swapping to handle memory contention among
processes. Processes are swapped out until enough memory is available.
The process is either in the memory or on the disk.
• Decisions regarding which processes to swap in or out are made by the
scheduler process. The scheduler wakes up at least once every 4
seconds to check for processes to be swapped in or out
• A process is more likely to be swapped out if it is idle, has been in
main memory a long time or it is large
• A process is more likely to be swapped in if it has been swapped out a
long time, or is small
Unix Memory Management
• Berkeley introduced paging to UNIX. Paging is added in order to handle
a large programs . The basic idea is : some programs don’t need entirety
bring into memory to run. Such as text, data. We can bring them to memory
by dynamic. When we need them, we can bring in.
• Paging can eliminate the external fragmentation of memory. Pagereplacement algorithm can keep enough free frames to support the
executing processes.
Window NT File System
• The fundament entity in NTFS is a volume. A volume is created by the
NT disk administrator utility, and is based on a logical disk partition. The
volume may occupy a portion of a disk, may occupy an entire disk, or
may span across several disks. In NTFS, all information about the volume
are stored in a regular file.
• NTFS does not deal with individual sectors of a disk, but instead uses
clusters as the unit of disk allocation. A cluster is a number of disk sectors
that is a power of 2. The cluster size is configured when an NTFS file
system is formatted.
Window NT File System
• A file in NTFS is a structured object consisting of attributes. Each
attribute of a file is an independent byte stream that can be created,
deleted, read, and written.
• Every file in NTFS is described by one or more records in an array
stored in a special file called the master file table (MFT). The size of a
record is determined when the file system is created.
Windows NT Memory Management
• The virtual-memory portion of the NT executive is the virtual-memory
manager(VM)
• The VM manager in NT uses a page-based management scheme with a
page size of 4KB. Pages of data that are assigned to a process but are not in
physical memory are stored in the paging file on disk
• The VM manager uses 32 bit addresses, so each process has a 4 GB virtual
address space. The upper 2GB is identical for all processes, and is used by
NT in kernel mode. The low 2 GB is distinct for every process, and is
accessible by both user-and kernel mode threads
Windows NT Memory Management
The NT VM manager uses a two-step process to allocate
memory. The first step reserves a portion of the process’s
address space. The second step commits the allocation by
assigning space in the NT paging file.
•
• The VM manager allows a privileged process to lock
selected pages in physical memory thus ensuring that the
pages will not be swapped out to the paging file
FILE SYSTEM
UNIX
• Hierarchical file
structure
• File and Directory
• Block
• Inode
WINDOWs NT
• NTFS
• Volume
• Clusters
• MFT(master file table)
Memory Management
UNIX
• Swapping
• Paging
WINDOWs NT
• Virtual-memory
manager(VM)
• Paging File
Conclusion
UNIX
• Mature and cheaper
• Reliability
• Configuration do not
require a shutdown and
reboot
• Can setting keyboard and
mouse
NT
• Immature And Expensive
• Set up e-mail by separate
software
• Slow
• More crash than UNIX
• Less stability than UNIX