NetApp Partition Alignment

Partition Alignment

Virtual machines store their data on virtual disks. As with physical disks, these virtual disks contain storage partitions and file systems, which are created by the VM’s guest operating system. In order to ensure optimal disk I/O within the VM one must align the partitions of the virtual disks to the block boundaries of VMFS and the block boundaries of the storage array. Failure to align all three of these items will result in a

dramatic increase of I/O load on a storage array and will negatively impact the performance of all Virtual Machines being served on the array.

The impact of mis-aligned partitions

Failure to properly align the file systems within Virtual Machines has a negative impact on many aspects of a Virtual Infrastructure. Customers may first notice the impact of misalignment with virtual machines running high performance applications. The reason for this is every I/O operation executed within the VM will require multiple I/O operations on the storage array.

In addition to the negative performance impact storage savings with NetApp Data Deduplication will be negatively impacted, reducing the total amount of storage savings. Finally, storage arrays will be over taxed and as the Virtual Infrastructure grows the storage array will require hardware upgrades in order to meet the additional I/O load generated by this misalignment. Simply put, one can save their company a significant amount of money by optimizing the I/O of their VMs.

Verifying partition alignment with windows operating systems

To verify the starting partition offset for a windows based virtual machine log onto the VM and run the System Information utility (or msinfo32). There you will be able to find this setting). To run msinfo32, select Start > All Programs > Accessories > System Tools > System Information.