Category Archives: General vSphere

Memory States

Host memory is a limited resource. VMware vSphere incorporates sophisticated mechanisms that maximize the use of available memory through page sharing, resource-allocation controls, and other memory management techniques. However, several of vSphere Memory Over-commitment Techniques only kick-in when the host is under memory pressure.

Memory States

Active Guest Memory

Amount of memory that is actively used, as estimated by VMkernel based on recently touched memory pages so it is what the VMkernel believes is currently being actively used by the VM.

Continue reading

ESXi and VM CPU Performance Issues

The following is a description of some common ESXi and VM CPU Performance Issues:

High Ready Time

Ready Time above 10% could indicate CPU contention and might impact the Performance of CPU intensive application. However, some less CPU sensitive application and virtual machines can have much higher values of ready time and still perform satisfactorily.

High CoStop (CSTP) Time

CoStop time indicates that there are more vCPUs than necessary, and that the excess vCPUs make overhead that drags down the performance of the VM. The VM will likely run better with fewer vCPUs. The vCPU(s) with high CoStop is being kept from running while the other, more-idle vCPUs are catching up to the busy one.

Continue reading

vCPU States

vCPUs are always in one of four states (vCPU States):


WAIT – This can occur when the virtual machine’s guest OS is idle (Waiting for Work), or the virtual machine could be waiting on vSphere tasks.  Some examples of vSphere tasks that a vCPU may be waiting on are either waiting for I/O to complete or waiting for ESX level swapping to complete. These non-idle vSphere system waits are called VMWAIT.

Continue reading

Removing VMFS Datastores from ESXi5.5 with VSAN

ESXi 5.5 and above stores coredumps on a datastore attached to the host, it can also create a vsantraces directory. Both of these can lock the datastore and prevent it from being deleted.

To check for and remove the coredump file do the following:

esxcli system coredump file list Path                               
Active  Configured       Size
-------------------------------------  ------  ----------  ---------
/vmfs/volumes/xx/vmkdump/xxx.dumpfile   false       false  702545920
/vmfs/volumes/xxx/vmkdump/xxx.dumpfile    true        true  702545920
/vmfs/volumes/xxx/vmkdump/xxx.dumpfile   false       false  702545920

The output shows that there are 3 dump files which are blocking the datastore. Only the owning ESXi host can disable and delete them, so you have to find out which ESXi is responsible for each file:

Continue reading