Configuring two or more hard drives in a RAID (Redundant Array of Inexpensive Disks) setup can increase performance and/or provide automatic protection against data loss from drive failure. RAID used to be expensive, hard to implement, and limited to businesses with dedicated IT departments. Now, motherboards in most desktop PCs support RAID, and Windows 7 provides software RAID that requires no special hardware at all. The technology is easily within the reach of the wallet and skills of any reasonably tech-savvy PC user.
What type of RAID do I want?
RAIDcomes in a number of flavors–or levels–that offer data protection,enhanced performance, or both. In addition to the seven core levels(RAID 0 through RAID 6), you’ll encounter a number of variants andcombinations. Some controllers (and dedicated external storage and NASboxes) can layer and even abstract RAID levels, allowing you to mix andmatch different capacity drives and add capacity without any additionalconfiguration.
Here are a few of the RAID levels you’ll find on affordable,consumer-level RAID adapters, motherboard chipsets, and Windowssoftware RAID:
JBOD (extend, spill over): JBOD, or Just a Bunch Of Disks simply allowsyou to extend a volume (drive letter, e.g. C:\) onto other disks. Datais written to the first disk until it’s full, then to the second disk,then the third, etc. It offers no boost in performance or redundancyand is a holdover from the days when smaller disks had to be chained tohandle large amounts of data. It’s largely irrelevant given today’smore capacious hard drives.
RAID 0 (Striping): This setup increases hard-drive performance bysplitting, or striping, data across two drives. By leveraging two databusses, data can be read and written more quickly. Unfortunately, RAID0 provides no data protection–in fact, itactually increases the chances of data loss since the failure of eitherdrive in the array results in the loss of the data stored on bothdrives. RAID 0 setups are standard on high-end gaming PCs and graphicdesign workstations, and provide a measurable, albeit modestperformance boost for hard-disk-intensive programs.
RAID 1 (Mirroring): A RAID 1 setup protects data from drive failure bysimultaneously writing the same data to two hard drives. Since eachdrive is an exact duplicate of the other, you can continue working ifone fails. RAID 1 offers no gain in performance and effectively reducesavailable capacity by half — two 2TB drives provide only 2TB ofstorage.
RAID 5 (Distributed Parity): Though you get both faster diskperformance and data protection from this setup, it requires a minimumof three hard drives. Instead of using an entire hard drive as abackup, RAID 5 spreads redundancy information–called paritybits–across all of the array’s drives. Where RAID 1 requires 50% ofavailable storage for redundancy, RAID 5 requires only 33%.
When one of the drives in a RAID 5 array fails, the data content ofthat failed drive is reconstructed using the parity bits on thesurviving drives and written to a new, replacement drive. The array isstill usable in the meantime.
RAID 1+0, 0+1, 10: Some adapters combine (referred to as nesting) RAID0 and RAID 1 to provide both data redundancy and increased diskperformance. This works by either striping data across a pair of drivesthen mirroring (0+1) them with another pair, or striping data acrosstwo mirrored pairs (1+0, aka 10). RAID 0+1, 1+0, and 10 require aminimum of four hard drives.
What do I need to set up RAID?
A Fresh Backup (existing data only): If you’re installing andconfiguring hardware RAID on a fresh system with no OS (your bestoption), or are adding disks for a separate array, skip this.Otherwise, back up your important data. Best practice is to have threecopies of your data: the original, a backup, and a backup of thebackup, preferably offsite.
If you have existing data that you want on the array, you’ll need toback it up, then restore it from a backup you make before creating yourarray–a process that writes new data to your hard drives regardless of what’s there. This is not necessary with Windows software RAID 0, however, it’s far faster than letting Windows re-sync (copy the data to) the mirror in the background.
Transferring an existing operating system is tricky, and with olderversions of Windows, sometimes impossible. See “Transferring ExistingWindows Installations to RAID” on the next page for instructions.
Windows Software RAID: Starting with Windows XP, Microsoft integratedRAID functionality into its operating systems. What type depends on theflavor of Windows:
- Windows XP allows spanned volumes(one volume over two or more disks), aka JBOD.
- Windows Vista Ultimate allows JBOD and RAID 1 striping.
- Windows 7 Home allows JBOD and RAID 1 while Professionaland Ultimate add RAID 0 mirroring. Windows 2000 Professional also hasJBOD, 0, and 1.
- Windows Server operating systems from 2000 on have JBOD,0, 1, plus support for RAID 5 distributed parity.
Windows RAID offers several advantages. You can create arrays fromwithin Window Drive manager so there’s no BIOS to configure. It’s alsomore flexible with mirrors, allowing you to create them from existingvolumes containing data, as well as delete either half of a mirror withthe other remaining intact. You can mirror individual partitions,including partitions from different drives onto a single drive.
Though you’ll see a lot of talk about hardware RAID being faster, thisdiscussion predates modern CPUs which can easily handle the overhead.Windows RAID is actually quite fast.
RAID controller: If you don’t use software RAID, there’s hardware. Youprobably already have a RAID controller in your PC; many older midrangeand high-end motherboards come with secondary RAID controller, andnewer motherboard chipsets offer integrated RAID obviating the need foran additional controller. Check your PC or motherboard documentation tofind out if your motherboard supports RAID (and if so, which levels),and for specific installation instructions.
If your PC doesn’t have integrated RAID, you may use an adapter card.Basic PCI and PCIe adapters supporting RAID levels 0, 1, 10, andsometimes 5 can be found online for $100 or less. Adaptec, Promise and othervendors offer a wide selection of pricier, but more capable RAIDadapters with onboard cache and advanced features. If possible, buy acard that supports greater-than-2.2TB disks and 6Gbps SATA III.
Two or more hard drives: If you decide on Windows software RAID, youmay use any drives you choose. They need not be the same size if you’remirroring individual volumes, though it’s generally a good idea.
Back in the days of parallel ATA, it was a no-no to mix drives fromdifferent vendors on a RAID controller. Sometimes it would work–moreoften it wouldn’t. With the advent of SATA, mixing vendors is no longeras problematic.
Also, though there are controllers that allow mixing and matchingcapacities without losing storage space (using advancedparity techniques), these are still relatively rare. Using drives ofdifferent sizes usually results in total storage capacity that’s only amultiple of the smallest drive. For example, combining 500GB and 320GBdrives in RAID 1 would be 320GB * 2, or 640GB instead of 820GB.
In practice, you’ll save yourself a lot of time and sidestep possibleissues by building your array with identical hard drives–meaningdrives of the same make, model, and size. You need at least two drivesfor RAID 0 and 1, three drives for RAID 5, and four for RAID 0+1, 1+0,and 10.
Floppy drive (Windows XP-only): If you plan to install Windows XP onyour new array, you will need a floppy disk with your RAID adapter’sWindows drivers, and a floppy drive to read it–Windows’ installationwon’t install the drivers from an optical drive. Thankfully, thisincredibly annoying limitation of Windows XP doesn’t apply in WindowsVista and Windows 7 which can read driversfrom hard drives, flash drives, or optical media.
Tools: You’ll need a small, non-magnetic Phillips screwdriver to removeand replace the fastener screw that secures the adapter card to the PCchassis, as well as to install any new hard drives. You might also wanta simple grounding strap that attaches to your wrist; look for one atyour local computer store for less than $15. Alternatively, never touchexposed contacts or electronics.
How do I install a RAID adapter?
Here’s how to physically install a RAID adapter card in your PC. Ifyour motherboard already supports RAID, skip to “Configuring theAdapter” below.
1. Unplug your PC and position the case so that you can comfortablyreach into the interior. If you have a tower case, you’ll findinstalling an expansion card easier if you lay the case on its side.
2. Protect your PC’s delicate circuits from static electricity byproperly grounding yourself. If you don’t have the patience or time tobuy a grounding strap, at least make an effort to ground your body bytouching your PC’s case before touching the inside of your PC or anycomponent.
3. Locate an open PCI or PCI Express expansion slot and remove thecover bracket that blocks the slot’s access port on the back of thecase. Typically, a single screw secures the bracket.
4. Remove the adapter card from its packaging, handling the card by itsedges (not the edge connector on the bottom); avoid touching the chipsand circuitry on either face of the card.
5. Align the adapter card’s connector with the expansion slot andgently but firmly push down on the top edge until the card is securelyseated in the slot. Secure the card to the chassis with the existingscrew or other clamping mechanism.
6. Once the card is installed, install and connect the hard drives tobe used in the array.
7. Reassemble the PC and power it up.
Configuring the Adapter
Each RAID adapter has a firmware configuration program, unique to thatmake or model, that lets the user select the type of RAID array toinstall and choose which hard drives to include in the array. Sometimesthe RAID functionality is embedded in the motherboard’s BIOS. Refer toyour adapter or motherboard documentation to guide you through thespecific installation steps for your adapter.
- Typically, you launch the setup program for a RAIDadapter by pressing Ctrl-R, Ctrl-A, or some other key combinationduring the PC boot process. Watch the screen for a prompt, or checkyour adapter’s documentation. On some PCs you may have to press the Tabkey to see the boot messages and the prompt.
- If RAID is embedded in the BIOS, as with many Intel motherboards, you will needto launch the BIOS setup. This is typically done by pressing F2,Ctrl+S, Del or some other key combination.
- Choose the drives and create the array.
- If asked to select a stripe size or chunk size for a RAID0 or RAID 5 array, select the default size. Playing with these settingsmay increase performance for users with plenty of time and energy toexperiment.
Installing Windows and the AdapterDrivers
If you are installing Windows XP or 2000 onto your array:
1. Carefully watch the bottom of the screen at the beginning of thesetup process for the prompt, and press F6 if you need to install athird-party SCSI or RAID driver. Be quick: You have only a few secondsto press F6 and launch the installation process.
2. Wait for the screen that says ‘S=Specify Additional Devices’ in thelower-left corner. Press S.
3. When prompted, insert the floppy disk with the adapter’s driversinto the floppy drive and complete the driver installation. Once that’sdone, Windows should continue the Windows installation routine.
If you are installing Windows Vista or Windows 7 onto your array:
1. Choose Custom (Advanced) Installation.
2. When asked where to install Windows, if your RAID volume does notappear (Windows Vista and 7 do have some RAID drivers) click the LoadDriver button at the bottom of the dialog.
3. When prompted, insert the floppy disk, CD, or flash drive with theadapter’s drivers and complete the driver installation. Once done, youshould be able to see the drives attached to the RAID controller. Ifnot, you may have pointed to the wrong driver or the array hasn’t beencreated yet.
Transferring Existing Windows Installations to RAID
It can be difficult, and sometimes impossible to transfer an existingoperating system installation to a RAID array. It all depends on the hardware and Windows operatingsystem involved. Follow the steps below for the best chance of success.
Transferring Windows XP
1. Install or enable the RAID controller in your PC. Do NOT create anyarrays.
2. Boot to Windows and install the RAID drivers. If your boot drive isattached to the RAID controller (some storage controllers such asIntel’s Storage Matrix pull double-duty) you may not be able to boot.If that’s the case, you’ll either have to attach the boot drive to anon-RAID port or use a secondary RAID controller for the new array.Start over.
3. Create a backup image in a safe, accessible location (external harddrive, flash drive, hard drive not to be included in the array, etc.)of the entire hard drive containing the existing OS installation using Norton Ghost, Acronis True Imageor another program. Preferably one with bare metal restorecapabilities, i.e. driver support for hardware that wasn’t in use whenthe image was made.
4. Reboot and create your array. Preferably, with new disks whilekeeping your old disk as a backup.
5. Restore the image using the program you created it with. If yoursystem won’t boot, try again using the bare metal restore functions.
Transferring Windows Vista or Windows 7
1. Create an image of the hard drive containing the existing OSinstallation in a safe, accessible location (external hard drive, flashdrive, hard drive not to be included in the array, etc.) using Windowsbackup.
2. Reboot and enable/install the RAID adapter.
3. Create your array. Preferably, with new disks while keeping your olddisk as a backup.
4. Boot using your Windows Vista/7 installation disc,and select Repair your computer.
5. Click on Load drivers and following the prompts, load the RAIDdrivers and any drivers required for the device you backed up to.
6. Restore your system using the backup image you previously created.
Using Windows software RAID
Windows XP, Vista, and 7 all offer software RAID which is a more thanviable alternative to hardware, and easy to implement. Which levels areavailable with depend on your flavor of Windows
The basic procedure for implementing Windows RAID is as follows:
1. Open the Start Menu, right-click on Computer and select Manage.
2. Scroll down the tree on the right to Disk Management (under Storage)and click on it.
3. Right-click over the large drive icon to the left for operationsthat will affect the entire disk (extend, stripe, mirror, or RAID 5).Only what’s available on your version and possible with your disk setupwill be enabled. For some levels, a wizard will pop up. Follow theprompts. If the disk is not dynamic, this will automatically convert it.
4. On dynamic disks, right-click over a volume on the drive and you’llsee an option to mirror that individual volume (Windows 7Professional/Ultimate, Windows 2000 Professional, and Windows serverOS’s only).
Note: Depending on the amount of existing data, it can take anextremely long time for new Windows RAID mirrors to sync up, and diskperformance will suffer till the process is completed. It’s far fasterto back up your files, create new mirrored volumes, then restore the data. If you do optfor letting Windows sync all the data, keeping Drive Manager open andon top will speed up the process.