NAS

NAS

NAS device is optimized for the file serving functions such as storing, retrieving and accessing the files for the application or the clients, a NAS device is dedicated for the file serving such a general purpose server which has its own operating system the NAS device also have its own operating system for the file serving by using open standard protocols.

Benefits of the NAS

1.       Support one- to many and many –to- one access of the data, by which one NAS device can serve many clients at same time and one client, can connect to many NAS device simultaneously.by this efficient sharing of the files between the many clients.

2.       Improved efficiency as NAS device came into the picture the burden of file services got reduced from the general purpose server and so the bottle neck of the performance got reduced because now the NAS devices uses the operating system specialized for the file serving.

3.       Flexibility got improved as the same file can be accessed by the different client using different operating system, means the windows and UNIX server can access the same file from the NAS devices.

4.       Centrally storage saved the lot of space issue, by reducing the duplicate copy in different client s, now the file can we stored in NAS device and can be accessed by different clients.

5.       Centralized management also saved lot of time for managing the files and data.

6.       Because of failover capability on NAS device the high availability of data is there, means data is only every time.

7.       Security is also got improved by locking the file and keeping the user base authentication.

NAS I/O operations.

1.       The requestor packages the I/O request into TCP/IP packets and sends it to the NAS device through the network.

2.       The NAS devices receive the packet and break physical storage to block level I/O request and execute the request and then repack it back to the appropriate file protocol response (CIFS/NFS).

3.       And then the NAS head again pack the data in TCP/IP packets and send back the packet to the requestor through the network.

Factor Affecting the NAS performance and Availability

As NAS uses the IP for communication so the bandwidth, latency issues associated with IP affect the NAS performance.

     

  1.   Number of hops:  A large number of hops can increase latency because IP processing is required at each hop, adding to the delay caused at the router.

  2.   Authentication with a directory service such as LDAP, Active Directory, or NIS: The authentication service must be available on the network, with adequate bandwidth, and must have enough resources to accommodate the authentication load. Otherwise, a large number of authentication requests are presented to the servers, increasing latency. Authentication adds to latency only when authentication occurs.

  3.   Retransmission: Link errors, buffer overflows, and flow control mechanisms can result in retransmission. This causes packets that have not reached the specified destination to be resent. Care must be taken when configuring parameters for speed and duplex settings on the network devices and the NAS heads so that they match. Improper configuration may result in errors and retransmission, adding to latency.

  4.   Over utilized routers and switches: The amount of time that an over-utilized device in a network takes to respond is always more than the response time of an optimally utilized or underutilized device. Network administrators can view vendor-specific statistics to determine the utilization of switches and routers in a network. Additional devices should be added if the current devices are over utilized.

  5.   File/directory lookup and metadata requests:  NAS client’s access files on NAS devices. The processing required before reaching the appropriate file or directory can cause delays. Sometimes a delay is caused by deep directory structures and can be resolved by flattening the directory structure. Poor file system layout and an over utilized disk system can also degrade performance.

  6.   Over utilized NAS devices:  Clients accessing multiple files can cause high utilization levels on a NAS device which can be determined by viewing utilization statistics. High utilization levels can be caused by a poor file system structure or insufficient resources in a storage subsystem.

  7.   Over utilized clients: The client accessing CIFS or NFS data may also be over utilized. An over utilized client requires longer time to process the responses received from the server, increasing latency. Specific performance-monitoring tools are available for various operating systems to help determine the utilization of client resources