Objective 1.3 – Troubleshoot complex storage solutions

Perform command line configuration of multipathing options

There are three default Path select Policies (PSP) available.

Most Recently used (MRU)

The host picks a path at the time of boot and this path will remain active until its fails. When the default path fails it will automatically switch to the second path. When the original path becomes available again it will not revert or failback to the first path.

Round Robin

With this PSP the storage request is rotated and load balance through all “active paths” in the storage device.

Fixed

This is the default policy. If the preferred path is not set then the host picks a path on boot time, this can be changed manually. The path will remain active until its fails. When the default path fails it will automatically switch to the second path however when the original path becomes available again it will automatically revert or go back to the first path.

You can find the default Multipathing plug-in from CLI and GUI as well.

From CLI:

#esxcli storage nmp psp list

psp

From GUI:

From Webclient ->Home-> Storage-> Select your device (Datastore) -> Manage-> Settings -> Connectivity and Multipathing -> Select the Host -> Click “Edit Multipathing” Button.

psp2

The default SATP (Storage Array Type Plugin) for iSCSI or FC devices is VMW_SATP_DEFAULT_AA, if there is no SATP policy assign to a device the default PSP is VMW_PSP_FIXED.

To display the installed Multipathing plug-in in an ESXi host.

#esxcli storage core plugin list

psp3

Similarly you can find the default SATP plug-in on an ESXi host

#esxcli storage nmp satp list

psp4

Check the Multipathing of a Specific Device.

To find the default SATP and PSP setting for a device using both CLI or GUI:

From CLI:

#esxcli storage nmp device list

psp5

From GUI:

From Webclient ->Home-> Storage-> Select your device (Datastore) -> Manage-> Settings -> Connectivity and Multipathing -> Select the Host -> Click “Edit Multipathing” Button.

To change the Default Multipathing of a device.

There are two options available when come to change the default Multipathing policy. Multipathing policy can be configured on per device basis. But if you have lots of devices in the environment then you can change the default PSP of a SATP. It will automatically change the PSP to all devices which associated to that Storage array type policy (SATP) .

Change the PSP of a device

From CLI:

First Check the default PSP of a Device.

#esxcli storage nmp device list

psp6

Example: As you can see above we have “MRU” PSP Policy is configured which comes default with VMWARE.

Unfortunetely I don’t have enough spare NICs in my home lab to have two dedicated iSCSI physical NICs. However if I could… this is how I would change the PSP to Round Robin

#esxcli storage nmp device set –d naa.600140574ea19b1d3cc2d3d7dd8280d8 –P VMW_PSP_RR

From GUI.

From Webclient ->Home-> Storage-> Select your device (Datastore) -> Manage-> Settings -> Connectivity and Multipathing -> Select the Host -> Click “Edit Multipathing” Button.

psp7

Select your Multipathing from Drop Down and Click “OK”

Note how the LUN is greyed out… this is beause ESXi knows my lab setup won’t allow for round robin.

Change the default PSP of a SATP.

To change the PSP of the following SATP (VMW_SATP_DEFAULT_AA) to Round Robin which comes with default VWM_PSP_FIXED PSP Policy:

First check the default SATP plug-in in on a ESXi host

#esxcli storage nmp satp list

psp8

Now change it to Round Robin

#esxcli storage nmp satp set –s VMW_SATP_DEFAULT_AA –P VMW_PSP_RR

psp9

Verify the configured setting.

#esxcli storage nmp satp list

psp10

Change a multipath policy

From CLI:

First Check the default PSP of a Device.

#esxcli storage nmp device list

#esxcli storage nmp device set –d <LUNID>–P VMW_PSP_RR

#esxcli storage nmp device list

Troubleshoot common storage issues

Sometimes your ISCSI/FC LUN is not able to display into the vSphere. Following are the guideline to check the issue.

Check cable connectivity
Check routing settings
Check access control configuration (CHAP)
For software and dependent hardware iSCSI, check network configuration
Rescan your iSCSI initiator.
Troubleshooting Storage Adapters

If your storage adapters experience performance problems, use the esxcli storage san commands to identify the problems.

Use the esxcli storage san commands to obtain and display events and statistics for the adapters. You can analyze the commands’ output to identify adapter problems and to find appropriate solutions

Here is example of an ISCSI adapter.

#esxcli storage san iscsi stats get

iscsiget

Troubleshooting Solid-State Drives

Use only unformatted SSDs for virtual flash resource and Virtual SAN configuration.
When you install ESXi or use Auto Deploy to provision hosts, you can enable the auto-partitioning boot option to create partitions on your host. You have several options to prevent auto-partitioning from formatting local SSDs as VMFS.you can prevent this by following esxi advance settings autoPartition=TRUE and skipPartitioningSsds=TRUE
You can use PSA SATP claim rules to tag SSD devices that are not detected automatically.
Troubleshooting NFS Problem

Some time attempt to mount a NFS device and it did not mount. Always make sure that the underlying NFS server offers internationalization support. If the server does not, use only ASCII characters.

Troubleshooting Logfile

When you analyse ESXi host’s /var/log/vmkernel log files, you will see events or error messages that contain SCSI Sense codes