VSAN-Troubleshooting-Reference-Manual

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Diagnostics and Troubleshooting Reference Manual – Virtual SAN Checking host memory requirements The number of disk groups and the number of disks that can be supported in a disk group is directly related to the amount of host memory available on an ESXi host in the Virtual SAN Cluster. At a minimum, it is required that a host has at least 6GB of memory. This will allow you to create a single disk groups, with one flash device and one magnetic disk per host in hybrid configurations, or one flash cache device and one flash capacity device in all-flash configurations. However, with only 6GB of memory, there will be very little will be available for VMs to consume. If the Virtual SAN configuration requires a host to contain the maximum number of disks (7 magnetic disks x 5 disk groups in both all-flash and hybrid configurations), then the host must contain 32GB of memory. These guidelines are the same for Virtual SAN 5.5 and 6.0, as well as hybrid and all-flash configurations. One final consideration is that the amount of host memory also impacts the number of components that can be created on the Virtual SAN cluster. With 8GB of memory, the maximum number of components supported is 750/host. With 32GB, one can create the maximum number of components/host, which are 9,000. Components will be covered in greater detail later in this manual. Symptoms of host memory shortage A symptom when there is a lack of host memory is that the following error is displayed in the VMkernel log when you try to create a disk group. The operation itself fails silently in the vSphere web client in vSphere 5.5. The ESXi host VMkernel logs need to be examined to find the root cause of the problem: 2013-12-10T17:00:49.878Z cpu0:1000019952)WARNING: LSOMCommon: LSOM_GlobalMemInit:1000: Unable to create LSOM slabs 2013-12-10T17:00:50.290Z cpu0:1000019952)WARNING: PLOG: PLOG_InitDevice:145: Failed to initialize PLOG's memory: Admission check failed for memory resource 2013-12-10T17:00:50.296Z cpu0:1000019952)WARNING: PLOG: PLOGProbeDevice:3585: Failed to init PLOG device A similar error is thrown when trying to add new disks to a disk group: 2013-04-23T15:22:14.831Z cpu1:1000027564)WARNING: PLOG: PLOGInitAndAnnounceMD:3780: Unable to allocate or get recovered mpx.vmhba2:C0:T6:L0:2 state5257150e-b9d8-a627-4011-5a90cee6e862 failed Out of memory In 6.0, this behavior has been improved considerably and a warning is now displayed in the vSphere web client if a shortage of memory resources is encountered when trying to create a disk group. V M W A R E S T O R A G E B U D O C U M E N T A T I O N / 22
Diagnostics and Troubleshooting Reference Manual – Virtual SAN License check It is important to ensure that the Virtual SAN cluster is correctly licensed. The easiest way to do this is via the vSphere Web Client Licensing section. Ensure that there are enough licenses for each of the hosts in the cluster, and that licenses are not over-committed; in other words, ensure that there are enough licenses to cover all of the CPUs in all of the hosts in the Virtual SAN cluster. Note that hosts that are not contributing to the Virtual SAN datastore in the cluster, and are only consuming the storage, still require a valid Virtual SAN license. Note that Virtual SAN 6.0 introduces an additional license requirement for all-flash configurations. If you wish to use all-flash functionality, an additional all-flash license is required. V M W A R E S T O R A G E B U D O C U M E N T A T I O N / 23
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VSAN-Troubleshooting-Reference-Manual

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