A customer needs to select an appropriate Path Selection Policy (PSP) for their storage array. There is no requirement for a preferred path. The policy should not select a new path unless the current one fails.
Which PSP meets the requirement?
A. Fixed
B. Round Robin
C. Most Recently Used
D. Asymmetric Logical Unit Access
Correct Answer: C
Explanation/Reference:
Explanation:
To maintain a constant connection between a host and its storage, ESXi supports multipathing. Multipathing is a technique that lets you use more than one physical path that transfers data between the host and an external storage device.
In case of a failure of any element in the SAN network, such as an adapter, switch, or cable, ESXi can switch to another physical path, which does not use the failed component. This process of path switching to avoid failed components is known as path failover.
The Most Recently Used policy selects the first working path, discovered at system boot time. If this path becomes unavailable, the ESXi/ESX host switches to an alternative path and continues to use the new path while it is available. This is the default policy for Logical Unit Numbers (LUNs) presented from an Active/Passive array. ESXi/ESX does not return to the previous path if, or when, it returns; it remains on the working path until it, for any reason, fails.
Incorrect Answers:
A: The FIXED policy uses the designated preferred path flag, if it is configured. Otherwise, it uses the first working path discovered at system boot time.
If the ESXi/ESX host cannot use the preferred path or it becomes unavailable, the ESXi/ESX host selects an alternative available path. The host automatically returns to the previously defined preferred path as soon as it becomes available again. This does not meet the requirement that the policy should not select a new path unless the current one fails. Therefore, this answer is incorrect.
B: The Round Robin policy uses an automatic path selection, rotating through all available paths, enabling the distribution of load across the configured paths. This does not meet the requirement that the policy should not select a new path unless the current one fails. Therefore, this answer is incorrect.
D: Asymmetric Logical Unit Access is not a specific pathing policy. It is a storage array feature that enables the use of the Fixed path with Array Preference policy. However, the Fixed path with Array Preference policy has been removed from ESXi 5.0. For Asymmetric Logical Unit Access storage arrays with ESXi 5.x, the Most Recently Used or Fixed policies are used. Therefore, this answer is incorrect.
References:
http://pubs.vmware.com/vsphere-55/index.jsp#com.vmware.vsphere.hostclient.doc/GUID-DD2FFAA7-796E-414C-84CE-1FCC14474D5B.html
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1011340
Explanation/Reference:
Explanation:
To maintain a constant connection between a host and its storage, ESXi supports multipathing. Multipathing is a technique that lets you use more than one physical path that transfers data between the host and an external storage device.
In case of a failure of any element in the SAN network, such as an adapter, switch, or cable, ESXi can switch to another physical path, which does not use the failed component. This process of path switching to avoid failed components is known as path failover.
The Most Recently Used policy selects the first working path, discovered at system boot time. If this path becomes unavailable, the ESXi/ESX host switches to an alternative path and continues to use the new path while it is available. This is the default policy for Logical Unit Numbers (LUNs) presented from an Active/Passive array. ESXi/ESX does not return to the previous path if, or when, it returns; it remains on the working path until it, for any reason, fails.
Incorrect Answers:
A: The FIXED policy uses the designated preferred path flag, if it is configured. Otherwise, it uses the first working path discovered at system boot time.
If the ESXi/ESX host cannot use the preferred path or it becomes unavailable, the ESXi/ESX host selects an alternative available path. The host automatically returns to the previously defined preferred path as soon as it becomes available again. This does not meet the requirement that the policy should not select a new path unless the current one fails. Therefore, this answer is incorrect.
B: The Round Robin policy uses an automatic path selection, rotating through all available paths, enabling the distribution of load across the configured paths. This does not meet the requirement that the policy should not select a new path unless the current one fails. Therefore, this answer is incorrect.
D: Asymmetric Logical Unit Access is not a specific pathing policy. It is a storage array feature that enables the use of the Fixed path with Array Preference policy. However, the Fixed path with Array Preference policy has been removed from ESXi 5.0. For Asymmetric Logical Unit Access storage arrays with ESXi 5.x, the Most Recently Used or Fixed policies are used. Therefore, this answer is incorrect.
References:
http://pubs.vmware.com/vsphere-55/index.jsp#com.vmware.vsphere.hostclient.doc/GUID-DD2FFAA7-796E-414C-84CE-1FCC14474D5B.html
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1011340