My Mac Pro 4.1 (circa 2009) has a MacPro Raid Card and the software shows two storage volumes - one 1TB SAS disk and one 2 TB SAS RAID volume.

The removal of the Parallels volume leaves me with the following showing in Disk Utility:

APPLE RAID Card Media: 1 TB SAS Internal Physical Drive

____Macintosh HD 999.14 GB SAS Internal Physical Volume OS X Extended

APPLE RAID Card Media: 1.96 TB SAS Internal Physical Drive

____Untitled 1.96 TB SAS Internal Physical Volume OS X Extended


Some final context, I have repurposed this MacPro (formerly an R&D server) as a desktop. My most demanding application is Mathematica used for analytics of financial data.

As per request from comments:

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More info:

System Information/Hardware/RAID/Mac Pro RAID Card/Drives lists: Bays 1 through 4, each showing an Hitachi model HDE721010SLA330 1TB HD with a different serial number. So 4 1TB HDs.

System Information/Hardware/RAID/Mac Pro RAID Card/RAID Sets: RS1 (1TB) & RS2 (1.96 TB) Status on both reporting as Viable (Good)

Should the machine have both of the above APPLE RAID Card Media volumes?

Why aren't they the same size and how do I tell if I have RAID for protection or for speed?

Basically, can someone explain what the above information means and provide suggestions to set this up properly?

  • 1
    Please add the output of diskutil list entered in Terminal or system info given here: "About your Mac" -> More Info… -> "System Report… -> Hardware RAID/SAS/Storage.
    – klanomath
    Feb 27, 2016 at 14:38
  • 1
    I've made a general answer. If you pop the case open - do you have 4 drives installed? You could have 4 count of 1 TB drives - one as JBOD and the others as RAID 5. Or you could have three drives. Once JBOD and two striped.
    – bmike
    Feb 27, 2016 at 16:00
  • @bmike -- Just added info above. Looks like 4 1TB HDs
    – Jagra
    Feb 27, 2016 at 17:09
  • So it's likely you have one mirrored volume (two copies of the data) on Macintosh HD) and one striped volume (half the data goes to each drive) on Untited.
    – bmike
    Feb 27, 2016 at 17:21
  • @bmike -- Could I just simplify the machine? Can I get rid of the RAID card and just have the four 1TB drives? That might work pretty well for me. I could keep OS X & applications on 1, data on another, and use the others as back up (although I do both Time Machine and offsite backup as well. Thoughts?
    – Jagra
    Feb 27, 2016 at 17:26

1 Answer 1


The hardware RAID card is very different than the software raid so you'll want to dig into two specific tools:

  • System Profiler - RAID section under Hardware
  • RAID Utility

These two items will report the actual hardware states such as health, mirroring, degraded mode, etc... The RAID card hides the actual hardware from diskutil and Disk Utility so they are of less use than if you were doing a fusion drive or software RAID.

As to the proper setup - that really depends on which tradeoff you wish to make. Speed comes at the cost of reliability. Redundancy (or mirroring) can provide a speed up for reads but a slight slow down for writes. You'll also want to check the battery status and replace that as well as make sure you have backups of the data since RAID is not a backup but just a way to optimize for one aspect of storage over another.

Once you have a handle on the actual hardware and how the RAID card is using the drives, perhaps ask a follow on question on your options for changing things and/or a basic question asking what RAID 1 or 0 or 5 are if that's of concern.

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