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How VSC for VMware vSphere optimizes I/O performance of misaligned virtual machines

Virtual Storage Console for VMware vSphere provides a non-disruptive, interim solution for the performance penalty introduced by misaligned virtual machines. Rather than align the misaligned VMDKs, which requires downtime, VSC aligns the I/O without requiring downtime by offsetting the VMDKs within optimized datastores.

A virtual machine is misaligned when VMDK partitions do not align with the block boundaries of the storage system. As a result, the storage system might read or write to twice as many blocks of storage than is necessary.

VSC can scan datastores to determine which virtual machines are misaligned and, if possible, perform an online alignment by non-disruptively migrating the misaligned virtual machines to a datastore that is optimized for the VMDK layout. VSC optimizes the datastore by functionally aligning I/O to the offset of the largest partition.

Online alignment is a good choice for virtual machines that you cannot take offline. When possible, you should take the virtual machine offline and physically align the VMDK using a tool such as VMware vCenter Converter.