How to achieve I/O alignment using LUN OS types
To achieve I/O alignment with your OS partitioning scheme, you should use the recommended ONTAP LUN ostype value that most closely matches your operating system.
The partition scheme employed by the host operating system is a major contributing factor to I/O misalignments. Some ONTAP LUN ostype values use a special offset known as a
prefixto enable the default partitioning scheme used by the host operating system to be aligned.
Note
In some circumstances, a custom partitioning table might be required to achieve I/O alignment. However, for ostype values with a 0 , a custom partition might create misaligned I/O.
prefixvalue greater than
The LUN ostype values in the following table should be used based on your operating system.
| LUN ostype | Prefix (bytes) | Prefix (sectors) | Operating system |
|---|---|---|---|
| windows | 32,256 | 63 | Windows 2000, 2003 (MBR format), 2008 and later |
| windows_gpt | 17,408 | 34 | Windows 2003 (GPT format) |
| windows_2008 | 0 | 0 | Windows 2008 and later |
| hyper_v | 0 | 0 | Windows 2008 Hyper-V and later |
| linux | 0 | 0 | All Linux distributions |
| xen | 0 | 0 | Citrix XenServer |
| vmware | 0 | 0 | VMware ESX |
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