VSAN-Troubleshooting-Reference-Manual

Diagnostics and Troubleshooting Reference Manual – Virtual SAN
18. Engaging with Global Support Services
If you are unable to root-cause an issue with a Virtual SAN deployment, be it a
failure of some components or a performance issue, always consider reaching out to
VMware’s Global Support Services organization for additional assistance. This
section of the troubleshooting reference manual will give some details on how to be
prepared when logging a Service Request. The more information that can be
provided to the technical support engineer, the sooner a resolution will be found.
Ensure scratch and log files are on persistent media
Virtual SAN supports ESXi booting from USB, SD and, in Virtual SAN 6.0, SATADOM.
However when booting from these devices, the scratch partition that is used for
storing logs is placed on RAM disk which means that they are not persisted if the
host is rebooted. The scratch partition is used for storing log files, such as
/var/log/vmkernel. A best practice recommendation is to place these logs on
persistent storage. VMware KB article 1033696 has details on how to redirect
scratch to a persistent datastore.
It is recommended that you do not use the VSAN datastore for persisting logs. If you
have configured your ESXi hosts to use the Virtual SAN datastore for the scratch
partition, then any issues that impact the Virtual SAN datastore will also impact the
ESXi hosts, as the host will be unable to save logs. It also means that previous logs
might not be accessible. This will make troubleshooting and diagnosis of the
underlying issue extremely difficult.
Do not use the Virtual SAN datastore as a scratch partition for ESXi hosts. Ideally use
a persistent datastore, such as a VMFS volume or NFS volume, for persisting log files.
Another best practice is to use a syslog server, which is discussed shortly.
Ensure VSAN Trace files are on persistent media
VSAN trace files should be stored on persistent storage. If your VSAN trace files are
not currently on persistent storage (e.g. when using USB/SD/SATADOM boot media,
which places these traces on a RAM Disk), you can use following command to
redirect the traces to persistent media.
# esxcli vsan trace set --help
Usage: esxcli vsan trace set [cmd options]
Description:
set
Configure VSAN trace. Please note: This command is not
thread safe.
Cmd options:
-f|--numfiles= Log file rotation for VSAN trace files.
-p|--path= Path to store VSAN trace files.
-r|--reset
When set to true, reset defaults for VSAN trace files.
-s|--size= Maximum size of VSAN trace files in MB.
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