Create a disk set
Create a Redundant Array of Independent Disks (RAID) set to optimize storage performance and increase reliability in case of a disk failure. You can also create a set that concatenates smaller disks to act as one larger disk.
Click the File menu, then choose RAID Assistant.
Select a set type:
Striped (RAID 0) set: A striped RAID set can speed up access to your data. You can’t create a RAID set on your startup disk; you must first start up your computer from another disk.
Mirrored (RAID 1) set: Protect your data against hardware failure with a mirrored RAID set. When you create a mirrored RAID set, your data is written to multiple disks so the information is stored redundantly. You can’t create a RAID set on your startup disk; you must first start up your computer from another disk.
Concatenated (JBOD) set: Increase storage space with a concatenated disk set. If you need one large disk, but you have only several smaller disks, you can create a concatenated disk set to use as one large disk.
Click the checkboxes of the disks you want to include in the set.
For each disk, click the pop-up menu in the Role column and choose “RAID slice” or “Spare” to designate the disk as a standard member or spare in the set, then click Next.
Enter a name for the RAID set in the RAID Name field.
Click the Format pop-up menu, then choose a volume format that you want for all the disks in the set. (For more information, see File system formats available in Disk Utility.)
Click the “Chunk size” pop-up menu, then choose a disk chunk size that you want used for all the disks.
When you create a striped set, chunks of data from the same file are distributed across the drives. Ideally, you want data distributed across drives evenly and at an optimum size so that it can be efficiently accessed. If you want high data throughput from your set, choose a smaller chunk size so that data is spread across the drives and one drive can be accessing data while another is seeking the next chunk. With mirrored disk sets, choose a chunk size that matches the data you’re accessing. For example, when working with video files, your Mac is accessing large chunks of data, whereas when using a database of many small records, your disks may be accessing smaller chunks of information.
If you are creating a mirrored RAID set, select the “Automatically rebuild” checkbox to allow the set to be automatically rebuilt when member disks are reconnected.
If you have a Mac Pro with a Mac Pro RAID card, use RAID Utility. It uses the RAID card for better performance and to create more types of RAID sets.