When you want to quickly resolve problems with the storage, you must understand the architecture. There is a big difference between NFS and VMFS filesystems or if DAS, FC, FCoE, iSCSI or new vSAN or VVOL are used. A great friend will be esxcli storage and esxcli iscsi for special use with iSCSI storage only.  

A problem you may need to analyze is the space occupied on the datastore. Use the command df -h:

[root@esxdell1:~] df -h
Filesystem Size Used Available Use% Mounted on
VMFS-5 1.8T 406.2G 1.4T 22% /vmfs/volumes/esxdell1_datastore1
VMFS-5 900.0G 828.5G 71.5G 92% /vmfs/volumes/NETAPP_NSX_iSCSI
vfat 285.8M 205.9M 80.0M 72% /vmfs/volumes/5559de5a-7b1a20ef-ed91-0010868226e8
vfat 249.7M 178.5M 71.3M 71% /vmfs/volumes/8f8f587c-516422b7-d925-07d7806f7725
vfat 249.7M 178.3M 71.4M 71% /vmfs/volumes/2ecc137e-08e991b9-05cf-022195dd8353
vfat 4.0G 512.0K 4.0G 0% /vmfs/volumes/59863b3d-88e9d712-04c5-0010868226e8

To solve a problem with the LUN or LAN connectivity the esxtop tool is what you can use with parameters u, d or v.

• With parameter u, the output will be as follows:

10:21:00pm up 34 days 12:52, 956 worlds, 14 VMs, 33 vCPUs; CPU load average: 0.50, 0.47, 0.46
 
DEVICE PATH/WORLD/PARTITION DQLEN WQLEN ACTV QUED %USD LOAD CMDS/s READS/s WRITES/s MBREAD/s MBWRTN/s DAVG/cmd KAVG/cm
naa.60a98000534b48755835373756324f2f - 128 - 0 0 0 0.00 4.58 0.19 4.39 0.00 0.01 0.73 0.0
naa.644a8420210904001cc39b5814256147 - 32 - 0 0 0 0.00 583.46 0.57 582.89 0.00 20.21 16.52 2.3

• With parameter d, the output will be as follows:

ADAPTR PATH NPTH CMDS/s READS/s WRITES/s MBREAD/s MBWRTN/s DAVG/cmd KAVG/cmd GAVG/cmd QAVG/cmd
vmhba0 - 1 11.44 0.00 11.44 0.00 0.07 0.27 0.01 0.28 0.00
vmhba1 - 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
vmhba2 - 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
vmhba64 - 1 7.63 0.00 7.63 0.00 0.03 0.51 0.01 0.51 0.00

• With parameter v, the output will be as follows:

GID VMNAME VDEVNAME NVDISK CMDS/s READS/s WRITES/s MBREAD/s MBWRTN/s LAT/rd LAT/wr
15715 EDGE-VIP-1 - 2 2.86 0.00 2.86 0.00 0.02 0.000 2.159
24914 EDGE-VIP-0 - 2 1.53 0.00 1.53 0.00 0.00 0.000 0.673
33673 EDGE-B-0 - 2 1.14 0.00 1.14 0.00 0.00 0.000 0.708
42640 NSX_Controller_ - 1 5.53 0.00 5.53 0.00 0.06 0.000 2.688
50799 NSX_Controller_ - 1 118.64 0.00 118.64 0.00 0.97 0.000 24.871
705902 vrni-platform - 1 15.26 0.00 15.26 0.00 0.13 0.000 1.740
708709 vrealize-automa - 4 14.31 0.00 14.31 0.00 0.12 0.000 0.691
712324 LogInsight - 3 34.33 0.19 34.14 0.00 0.38 29.899 2.275
716883 App01 - 1 0.00 0.00 0.00 0.00 0.00 0.000 0.000
717674 DB01 - 1 0.00 0.00 0.00 0.00 0.00 0.000 0.000
717682 App02 - 1 0.00 0.00 0.00 0.00 0.00 0.000 0.000
717706 Web01 - 1 0.00 0.00 0.00 0.00 0.00 0.000 0.000
83831097 desktop-ubuntu - 1 0.00 0.00 0.00 0.00 0.00 0.000 0.000
142397216 Guest Introspec - 1 0.00 0.00 0.00 0.00 0.00 0.000 0.000

To change in the configuration view, use the parameter f and set what you need to see.