VSAN-Troubleshooting-Reference-Manual

Diagnostics and Troubleshooting Reference Manual – Virtual SAN
Navigating VSAN Observer – VSAN Disks
The next tab is the VSAN Disks view. As mentioned previously, this is where disk
bottlenecks can be observed, which in turn might be impacting VM performance. All
the same counters and metric observed in the VSAN client view are shown here.
However, where the VSAN Client gives the client side view (nodes with VMs
requesting information), VSAN Disks can be thought of as the server side view
(nodes where requested information resides).
The top-most layer in Virtual SAN is the VSAN Client layer. Beneath the VSAN Client
layer is the VSAN Disks layer. This layer is responsible for all of the physical disks in
each host. The VSAN Disks view shows the VSAN statistics of the physical disk layer
of each host. This is the layer that actually serves I/O from local disks to different
nodes in the cluster.
Due to the distributed nature of VSAN the physical disks of one host may be
accessed by VMs on all hosts in the VSAN cluster. Because a VM may not reside on
the same node as it’s storage on Virtual SAN, the Virtual SAN disks layer is shown
from the node where the data resides, and it serves the data over the network to the
requesting node (client).
To correlate the client view with a disk view, you would need to use the VMs view,
which will be discussed shortly.
The VSAN Disks tab shows statistics related to physical disks in each host, so it
includes all disk group performance from that host in a single view. This tab
provides a reasonable insight into the performance of the physical disks in every
host in the cluster.
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