Xsan supports LUN sizes of 2 TB or smaller. However, if you're using an Xserve RAID that provides LUNs larger than 2 TB (such as Xserve RAID installations that use 500 GB hard drives), you can use RAID Admin to create RAID sets that are smaller than 2 TB by using a feature known as slicing.
In the diagram, the 3.5 TB LUN that comprises the drives on the left side of the Xserve RAID (controlled by the upper controller) has been sliced into two LUNs (LUN1, LUN2); the 3.5 TB LUN that comprises the drives on the right side of the Xserve RAID (controlled by the lower controller) has also been sliced into two LUNs (LUN3, LUN4). It is recommended to slice the available storage into as few slices as possible. When creating pools in Xsan Admin, you would create two pools in this example.
In this example, assume that the metadata and journaling pool is located on a separate Xserve RAID. Choose Fill as the Allocation Strategy for the Volume when using the slicing method. For tips on correlating LUNs to RAID slices, please refer to Lesson 8. |