Information in this article applies to macOS Big Sur (11) through macOS Sierra (10.12).
In some cases, they do a better job.
Why Use RAID?
RAID arrays can solve some problems you may experience with your Mac’s current storage system.
RAID 0 can be used to boost performance at a reasonable cost.
If you have data on these disks that you want to keep, back up the data before proceeding.
The speedier you want to go, the greater the risk of failure.
You should havea backup plan in placeif you’re creating a striped RAID array.
LaunchDisk Utility, located at /Applications/Utilities/.
verify the two disks you wish to use in the RAID array are present in the Disk Utility sidebar.
SelectRAID Assistantfrom the Disk UtilityFilemenu.
In the RAID Assistant window, selectStriped (RAID 0)and then selectNext.
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The RAID Assistant displays a list of available disks and volumes.
Select at least two disks.
you might also select aChunk size.
The chunk size should loosely match the predominant size of data your array will be handling.
A window appears, asking you to confirm that you want to create the RAID 0 array.
Disk Utility creates your new RAID array.
In the Disk Utility sidebar, pick the striped array you want to remove.
The key in should say “RAID Set Volume.”
Just above the Info panel is aDelete RAIDbutton.
If you dont see the button, you may have the wrong disk selected in the sidebar.
A window drops down, asking you to confirm the deletion of the RAID set.
Another window drops down, showing the progress for deleting the RAID array.
Once the process is complete, selectDone.
It’s a good idea toerase and format all the disksthat were part of the deleted array.
This section looks at creating and managing a RAID 1 array, also known as a mirrored array.
LaunchDisk Utility, located in/Applications/Utilities/.
Confirm that the disks you intend to use in the mirrored array are listed in the Disk Utility sidebar.
The disks don’t need to be selected, but they need to be present in the sidebar.
A list of disks and volumes displays.
pick the disk or volume you want to be part of the mirrored array.
Make your selections and then selectNext.
The RAID Assistant prompts you to set the properties of the mirrored RAID set.
Use 64K for arrays that will house general data and operating systems.
Use a larger chunk size for arrays that store images, music, or videos.
Use the smaller chunk size for arrays used with databases and spreadsheets.
Mirrored RAID sets can also be configured to automatically rebuild the array when a slice fails or is disconnected.
SelectAutomatically Rebuildto ensure optimum data integrity.
Be aware that automatic rebuild can cause your Mac to operate slowly while the rebuild is in process.
Make your selections and then chooseNext.
You’re about to erase and format the disks associated with the RAID array.
All data on the disks will be lost.ensure you have a backupof any content on those disks before continuing.
A window drops down, asking you to confirm that you want to create the RAID 1 set.
The RAID Assistant displays a process bar and status as the array is created.
When it is complete, selectDone.
You may want to do this to increase reliability or to replace older slices that are showing issues.
In the Disk Utility sidebar, go for the RAID 1 (Mirrored) disk.
The bang out should read “RAID Set Volume.”
A window appears, listing available disks and volumes that can be added to the mirrored array.
Select a disk or volume and then selectChoose.
A window drops down to confirm you’re about to add a disk to the RAID set.
The sheet displays a status bar.
Once the disk has been added to the RAID, selectDone.
Disks that are removed from a RAID 1 mirror usually have the data preserved.
This allows you to archive the data in a safe location without disturbing the RAID array.
For the data to be retained, the file system on the removed slice needs to be resizable.
If the resizing fails, all data on the removed slice is lost.
opt for RAID array from the Disk Utility sidebar.
The Disk Utility window displays all the slices that make up the mirrored array.
go for the slice you want to remove and then select theminus(-) button.
The sheet displays a status bar.
When the removal is complete, selectDone.
However, Repair has an entirely different meaning here.
grab the mirrored array in the Disk Utility sidebar.
Just above the Info panel, selectDelete RAID.
A window drops down, warning you that you’re about to delete the RAID Set.
Disk Utility attempts to break the RAID array apart while preserving the data on each RAID slice.
There is no guarantee of the data being intact after the deletion of the RAID array.
If you need the data, perform a backup before selectingDelete.
The sheet displays a status bar as the RAID is removed.
When it is complete, selectDone.
The most common compound RAID array is aRAID 10or RAID 01 array.
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This example creates a RAID 10 set using Disk Utility and the RAID Assistant.
The reliability improvement comes at the cost of doubling the number of disks needed.
With the first mirrored pair created, repeat the process to create a second mirrored pair.
For ease of understanding, you may want to give the mirrored arrays names, such asMirror1andMirror2.
At this point, you have two mirrored arrays namedMirror1andMirror2.
The important step in the process is to selectMirror1andMirror2as the disks that will make up the striped array.
Technically, it isn’t a recognized RAID level, as RAID 0 and RAID 1 are.
Nevertheless, it’s a useful method of using multiple disks to create a single larger volume for storage.
JBOD Requirements
The requirements forcreating a JBOD arrayare loose.
JBOD arrays provide neither a performance increase nor a reliability increase.
As with all RAID arrays, having a backup plan is a good idea.
From the Disk UtilityFilemenu, selectRAID Assistant.
In the RAID Assistant window, selectConcatenated (JBOD)and then selectNext.
you might select an entire disk or a volume on a disk.
Make your selections and selectNext.
Enter a name for the JBOD array, a format to use, and a Chunk size.
Be aware that chunk size has little meaning in a JBOD array.
The RAID Assistant creates the new JBOD array.
Once it is complete, selectDone.
LaunchDisk Utilityif it isn’t open.
In the Disk Utility sidebar, opt for JBOD array you created earlier.
To ensure you selected the correct item, check the Info panel.
The Typefield should read “RAID Set Volume.”
Select theplus(+) button located above the Info panel.
The disk is added, causing the available storage space on the JBOD array to increase.
Resizing the array in this manner requires that the partition map be recreated.
LaunchDisk Utilityand go for the JBOD array from the sidebar.
Disk Utility displays the list of disks that make up the array.
choose the disk you want to remove and select theminus(-) button.
You are warned about the possible loss of data should the process fail.
After the removal is complete, selectDone.
grab the JBOD array from the Disk Utility sidebar.
verify the punch in field under the Info panel reads “RAID Set Volume.”
After the JBOD array is removed, selectDone.
