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How to Create a Software RAID-01
See the RAID-1 mirroring page for a discussion.
Creating a software RAID-1 mirror in Disk Utility
Ouch! Apple removed all RAID from Disk Utility in OS X El Capitan—see the SoftRAID instructions further below.
This example shows a 2-drive RAID-1 mirror volume Master of capacity 4TB.
- Click the tab .
- Enter a and choose choose .
Leave the file system as . - Drag the desired drive icons at left (“4TB HGST....”) into the area at right (“New member: ...”). In this example, 2 drives of four are being used.
- Click .
It is possible to make a RAID out of partitions on each drive. First partition each drive identically, then follow the steps above for each RAID set.
As in steps #1/2/3/4 above:
Confirm the change. This will erase everything on the drives chosen, so be sure the correct drives have been chosen (risks of making a mistake go up with 4/6/10 drives!). The result is one 4TB volume consisting of two 4TB hard drives.
At any time later, confirm the RAID status by selecting the RAID set at left.
Confirming RAID-1 mirror status on a regular basis is important with Disk Utility mirror, because Disk Utility offers no reporting facility for a drive failure; it’s possible to run for months and have no inkling that a drive has failed. Put it into your calendar at least once a week!
Observe that the two hard drives are shown now with under each, and that the RAID itself is listed as , with volume under it. This confusing display has been present in Disk Utility for many years.
Creating a software RAID-1 mirror with SoftRAID
SoftRAID (see below) has a warning/reporting mechanism for failure of a RAID-1 drive, and it’s one reason to use SoftRAID over Disk Utility.
This example shows a 2-drive RAID-1 mirror volume Master of capacity 4TB.
- Choose .
- Enter a name in the text box.
- Select 2 or more drives to be used.
- Click .
The result as shown here is one 4TB volume consisting of two 4TB hard drives.
A smaller capacity could have been specified, leaving some space on each drive unused. The additional/remaining space not otherwise used can be used to make another RAID set or independent volumes in the same manner as above.
