ns2 project in jharkhand

ns2 project in jharkhand

     ns2 project in jharkhand by separating the IDD layer as a distinct process

from the rest of the layers, any communication to the

IDD layer can be done asynchronously. Requests for

I/O on a given host will be controlled by the IDD process

on that host. Furthermore, all 1/0 ns2 project in jharkhand requests can

be made non-blocking allowing the system to overlap

communication with 1/0 which, in lower-bandwidth

networks, results in great performance benefits.

In this section, we describe the ns2 project in jharkhand communication

strategies used during data access in VIP-FS. Three

strategies for data access have been incorporated into

VIP-FS: direct access, two-phase a.ccess, and assumed

requests. This will facilitate research ns2 project in jharkhand in data access

arid availability schemes – one of the primary objectibes

of the project. The direct access strategy is the traditional access

method used for parallel and distributed file systems.

In this scheme, every 1/0 request ns2 project in jharkhand is translated into

requests to the appropriate 1/0 device.

Each distributed application is composed of one or

more clients. The file syst,em services each client independently

of the others. There is no globally organized

access strategy as with the remaining two methods This scheme is used when each client obeys a

self-scheduled access pattern. distributed application perform

1/0 access with some global pattern, then it is

useful to employ a more efficient access strategy. l’he

two-phase access strategy has ns2 project in jharkhand been shown to provide

more consistent performance across a wider variety

of data distributions than direct access methods [7].

With two-phase access, all clients ns2 project in jharkhand access data approximately

simultaneously. The file system schedules access

so that data sotrage or retrieval from the devices follow a near optimal pattern with a reduction

in the total number of requests for the entire 1/0

operation. In a second stage, the data is buffered and

redistributed to conform with the data decomposition

used by the application (the target decomposition). The two-phase access strategy gains its effectiveness

by relying upon the existence (assumed) of a higher degree,

less congested interconnection networks between

clients versus the network used to access data to and

from the storage system; this is often the case in parallel

machines. However, in distributed systems, shared

media networks are commonly employed, and ns2 project in jharkhand the basis

for two-phase strategy’s improved performance is

lost. We have designed an alternative approach which

may significantly improve read performance by greatly

reducing the number of requests seen by each 1/0 device;

we call this the assumed-requests technique.

With assumed-requests, data decomposition information

is distributed to the IDD processes as part of

the file description information. Clients are assured

to make requests in a collective manner as in two phase access. That is, we assume a Single-Program-

Multiple-Data (SPMD) of computation. A one-to-one or many-to-one mapping is established from the set

of 1/0 devices to a subset of clients (the latter case

occurs when the number of 1/0 devices exceeds the

number of clients). We say that the members ns2 project in jharkhand of the subset are asszgned to the 1/0 devices.

When a read operation is performed by the application

program, only the assigned clients have their requests actually delivered to 1/0 devices. ‘Thus, each

1/0 device only receives a single request each. From the ns2 project in jharkhand  request the 1/0 device receives, along with data decomposition information, each 1/0 device computes bhe amount of data required by all clients (itssigned or not).