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SAS Drives Displays Two Different Capacity on Identical Systems

Knowledgebase Article

SAS Hard Drive shows two different capacity on two systems with exact same configuration SR2500ALLX (with key and RAM installed). One system shows, 278.875 GB while the second system displays 278.464 GB.

Drive Coercion refers to the ability of the Controller to recognize the size of the physical drives connected and then force the larger drives to use only the amount of space available on the smallest drive. Drive Coercion allows an option to map out a reserved space to compensate for slightly smaller drive sizes that may be added later. The default is set to 1 GB.

The Coercion algorithm options are:

  • None: No coercion of size.
  • 128 MB: The software rounds the drive capacity down to the next 128 MB boundary and then up to the nearest 10 MB until the coerced capacity is larger than the actual drive size. It is then reduced by 10 MB.
  • 1 GB: The software rounds the drive capacity down to the nearest 1 GB boundary and then down by 1 MB. This corresponds to the terms most drive manufacturers use.

To resolve the issue, set up both Controller's Coercion Mode setting in RAID BIOS Console 2 to "1GB". This should show accurate and similar capacity after saving the settings.


Intel Knowledge Base Article Disclaimer

Operating System:

OS Independent

This applies to:

Intel® Server Board S5000PAL
Intel® Server Chassis SR2500

Solution ID: CS-031893
Last Modified: 28-Oct-2014
Date Created: 12-Oct-2010
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