Veerendra kadganchi (MCA 2).
Roll no 31
Assignment 4
Q.1) Explain different file model in detalle File Model :-"
unstructured & structured files: - Two types for file modeling are structure &
modifiability.
Files models based on these criteria are described below. In unstructured model, there is no
substructure known to the file serves & the contents of each file of the file system, appeaes
to the file serves as an uninterpretedsequence of byte.
-In structured model, a record in the a file appeaks to the file served as an eed sequence of
records. Records of difint files of the same file system can be diffet size.
-In structured model, a record is the smallest unit of file data that can be accessed, and the
file system. read of write operations ace caccied out on a set of becords.
-structured files are again of two-types with non indexed records & files with indexed
decoecks. In the non-indexed record model, a file record is accessed by specifying its
position withing the file.
-In the indexed recoed model second have one or more key fields & can be addressed by
specifying the values. of the key fields.
In the file systems that allow indexed records, a le is maintained as a B-tree or other suitable
data structure of a hash table is used to locate beconds quickly.
2.Mutable & Immutable files :
According to the madifiability criteria, files are of two types ::
mutable &immutable.
Most existing system use the mutable file model. In this model, an update performed on a
file overwrites on its old contents to produce the new contents.
eg.a file is represented as a single stoced sequence the altered by each update opecation.
In immutable model, a file can not be modified once it has been created except to be
deleted. The file vessioning apptech is normally used to implement file updates, & each file
is represented by a history of Immutable versions
Q.2 What is file Replication & Distinguish between file Replication & file cachinge?
File Replication:
High availability is a desirable feature of a good distributed file system & file.. ceplication is
the primary mechanism for improving tile availability. A seplicated the is the multiple copies,
with each ropy located on a seperate file secuess.
Difference between Replication & caching & -
i) A ceplica is associated with a seeven, whereas a cached copy is normally associated with
a client.
Veerendra kadganchi (MCA 2).
Roll no 31
2 The existence of a cached copy is primarily dependent on the locality in a access patterns,
whereas the existence of a seplica normally depends on availability Land performance
requirements.
3) As compared to a cached copy, a replica more peast stent, widely known, secuce,
Nailable, complete & accurate.
4) A cached copy is contingent upon a replica only by peciodic devalidation with respect to a
replica can a cached copy by useful.
Q3) Waite Short note on Unix semantics--
A)Unix semantics--
In particulas, weites to an open file by a used immediately become visible to othes useds
who have this file open at the same time.
This semantics can be achieved in a distributed system by disallowing files to be cached at
client Dodes & allowing a shated file to be managed by only one file seovers that processes
all read & white requests for the file strictly in the order in which it receives them.
There is a active & possibility that, due to network delays. client requests from different
nodes may get processed at the served node in an different from the actual orded in which
the request where content made
B) Novel Netware
Novel Netware is type of network operating system. It provides wide networking Services
tanging from easy & simple file to the network uses, data, security, & even desquece
manage ment.
-It is generally designed for networks of LAN operating system.
-Novell netwate is most populas & widely used networksystem in PC world.
-It only needs low hardware requirements & has memory protection. It keeps safe & protects
single processes.from each other.
-Novell Netware is discontinued network operating system basically developed by Novell,
Inc.
Layers
Application SAP FILE SERVER ---
Transport NCP | SPX
Network IPX
Data link Ethernet Token Ring ARCnet
Physical Ethernet Token Ring ARCnet
tig. The Novell Netware Reference model
