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Why the actual LUN size is a little bigger than the specified size after “lun resize” sometimes?

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san
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Applies to

SAN

Answer

  • The actual LUN size being resized depends on the cylinder size.
  • Cylinder size varies according to OS type and LUN size.
  • When the specified size cannot be exactly divisible by the value of cylinder size, it increases the corresponding insufficient size.
  • Cylinder Size=Bytes per Sector*Sectors per Track*Tracks per Cylinder
  • The related information can be checked from LUN.xml in AutoSupport.

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Example:

Resize a LUN size to 1200MB whose cylinder size is 9MB.
1200/9=133.33333...MB
1200 can not be exactly divisible, an additional 6MB is needed.
So the actual LUN size is automatically changed to 1206MB.

Additional Information

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