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).