An I/O request – from start to finish
Now that we have a general understanding of how ESXi presents storage to a virtual machine and handles load balancing and failover, let's have a look at an I/O request from start to finish. The following figure shows a graphical representation of the following steps:
- The VM issues a SCSI request to its respective virtual disk.
- Drivers from within the guest OS communicate with the virtual storage adapters.
- The virtual storage adapter forwards the command to the VMkernel where the PSA takes over.
- The PSA loads the specific MPP (in our case the NMP) depending on the logical device holding the virtual machines disk.
- The NMP calls the associated PSP for the logical device
- The PSP selects the appropriate path to send ...
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