Adding storage to your Mac enhances its file capacity, but the specialized form called RAID can speed your system's performance, especially in applications that work with large files or make heavy use of scratch disk space. Although you can use the drives that support a RAID configuration with a third-party RAID card, Apple made several generations of these adapters for specific models of its desktop and network-server computers.
What RAID Does
RAID stands for "Redundant Array of Independent Drives" or "Redundant Array of Inexpensive Disks." It transforms multiple off-the-shelf hard drives into a large, fast storage mechanism that your operating system sees as one drive. You can set up RAID in five different levels, each with its own performance characteristics. RAID 0 shares file-access chores among a set of disks, striping chunks of a file on sequential mechanisms for high-performance access. If one drive fails, the entire data set becomes inaccessible. RAID 1 uses mirroring to echo data on more than one drive, protecting files against hardware failure. RAID 0+1 combines the performance and data-security attributes of levels 0 and 1, but stores only half as much data as its drive capacity. RAID 3 uses striping and redundancy, with less setup cost than RAID 0+1. RAID 5 also combines the attributes of levels 0 and 1, but emphasizes data-reading performance over data-writing. In all these scenarios, a RAID card installs in your computer and controls internal or external hard drives.
Mac Pro RAID
Apple made two versions of the Mac Pro RAID Card, issued at the same times as corresponding versions used in Apple's XServe servers. The 2007 generation of this PCI card uses a blue PCB board; the 2009 version features black. Unlike the XServe RAID Card, the Mac Pro version can't support drive hot swapping to replace RAID storage. The 2009 edition can support sleep, a low-power standby mode that the 2007 version can't accommodate.
Apple's XServe line of rack-mounted server systems included a RAID module that could hold up to 14 drives. The module connected to an XServe -- or a qualifying desktop Mac -- through the Apple Fibre Channel PCI Card, which provided high-speed data access. In addition to its optional RAID module, XServe also supported RAID through internal drives and an XServe RAID Card. The 2007 and 2009 versions of this PCI card offer compatibility with corresponding XServe generations.
Using Apple RAID Cards
OS X installs Apple's RAID Utility within the Applications folder's Utilities folder. After you connect hard drives to your computer's motherboard and insert the Apple RAID card in a PCI slot on your qualifying Mac Pro or XServe, restart your computer so the card can condition the backup battery that preserves cached data. Expect this process to require up to 12 hours; make sure to allow it to finish before you shut down or restart the computer. Use RAID Utility to set up drives and begin using them before the battery finishes charging, migrating an existing RAID from your startup drive or creating a new one. To complete a migration procedure, boot from your OS installation disc and use RAID Utility to transform your existing RAID set into an internal RAID 1 or RAID 5 configuration. To create a RAID from scratch, boot your computer from its startup drive and launch RAID Utility. The Create RAID Set command enables you to choose a configuration and turn drives into a RAID set, which behaves like a unified storage mechanism, so you can format a RAID on it. RAID Utility also can enlarge a volume without damaging RAID data, relocate volumes among various RAIDs, add drives to serve as spares, check the health of your RAID hardware and remove a RAID altogether.
Apple issued a RAID Card Firmware Update (see Resources) for Mac Pro RAID Cards with firmware versions M-188.8.131.52 and M-184.108.40.206 to M-220.127.116.11. Some Mac Pro models also required a firmware update (see Resources) before they could process the application that applied the RAID Card Update. The RAID Card update improved both cards' ability to maintain and report the status of their onboard batteries. It also enhanced startup, recovery and rebuilding operations, along with OS X compatibility.
- Macworld: Apple Adds Optional RAID Card to XServe
- Apple: RAID Utility User Guide
- Apple Support: Archived -- Xserve RAID Card: Identification and Compatibility
- Apple Support: Mac Pro (Early 2009) RAID Card: Identification and Compatibility
- Apple Support: Mac Pro (Mid 2012 and Earlier): Frequently Asked Questions About the Mac Pro RAID Card and Xserve RAID Card
- Apple Support: Mac Pro RAID Card: Capacity for Four-Drive RAID 5 Configurations May Be Different Than Expected
- Apple Support: Mac Pro RAID Card and Xserve RAID Card (Early 2009): Enabling System Sleep
- Apple Support: Archived -- About the Apple RAID Card Firmware Update 1.0
- Apple Support: Archived -- Mac Pro: Apple RAID Card Firmware Update 1.0 Reports EFI Firmware Update Is Required
- Apple Support: Archived -- Apple Fibre Channel PCI Card: About the Fibre Channel Status Indicators
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