NS0-162 Exam Dumps : NetApp Certified Data Administrator (ONTAP)

The space allocation option is a LUN attribute that enables the host to communicate with the storage system about the blocks that are no longer in use by the host file system. When the space allocation option is enabled, the host sends SCSI UNMAP commands to the storage system when files are deleted on the disk. The storage system then reclaims the space from the thin-provisioned LUN and makes it available for other LUNs or volumes. This process is also known as space reclamation or hole punching. If the space allocation option is disabled, the host does not send SCSI UNMAP commands and the storage system does not reclaim the space from the thin-provisioned LUN, resulting in a discrepancy between the host and the storage system. References :- Space reclamation, Enable or disable the space allocation option for a LUN

 To increase access security in both NFS and iSCSI environments, you can use Kerberos and CHAP as authentication methods. Kerberos is a network authentication protocol that uses tickets to provide mutual authentication between clients and servers. CHAP is a challenge-response protocol that verifies the identity of a peer by using a shared secret. ONTAP supports Kerberos for NFS exports, which allows you to secure NFS traffic with encryption and integrity checking. ONTAP also supports CHAP for iSCSI LUN access, which prevents unauthorized access to iSCSI targets and initiators. References :- NFS security overview, iSCSI Security Configuration

 According to the NetApp best practices, flow control should be disabled on data network ports and cluster network ports using 10GbE Ethernet. This is because flow control can cause excessive pause frames, xon/xoff frames, or packets being re-queued, which can affect the network performance and TCP throughput. Flow control works at the physical link layer and does not consider the upper level protocols. Therefore, it is recommended to disable flow control end-to-end on both data and cluster network ports for optimal performance. References :- How to modify flow control on cluster port in ONTAP, What are the flow control best practices for Ethernet?, Configure your network for best performance