Windows 7 / Getting Started

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Configuring RAID 0: Striping

RAID level 0 is disk striping. With disk striping, two or more volumes-each on a separate drive-are configured as a striped set. Unlike spanning, Windows breaks the data to be written into blocks called stripes and then writes the stripes sequentially to all disks in the set. So if there are three disks in the set, Windows writes part of the data to the first disk, part of the data to the second disk, and part of the data to the third disk-this process of alternating between the disks is called striping.

Although the boot and system volumes shouldn't be part of a striped set, you can place volumes for a striped set on up to 32 drives, but in most circumstances sets with 2 to 5 volumes offer the best performance improvements. When 3 to 32 drives are used, the major advantage of disk striping is speed. Data can be accessed on multiple disks using multiple drive heads, which improves performance considerably. When you try to use more than 32 drives, the performance improvement decreases significantly.

When you create striped sets, you'll want to use volumes that are approximately the same size. Disk Management bases the overall size of the striped set on the smallest volume size. Specifically, the maximum size of the striped set is a multiple of the smallest volume size. For example, if the smallest volume is 1 GB, the maximum size for a three-disk striped set is 3 GB.

You can maximize performance using disks that are on separate disk controllers. This allows the system to simultaneously access the drives. Keep in mind that this configuration offers no fault tolerance. If any hard disk drive in the striped set fails, the striped set can no longer be used, which essentially means that all data in the striped set is lost. You'll need to re-create the striped set and restore the data from backups.

You can create a striped set by following these steps:

1. In the Disk Management Graphical View, right-click an area marked Unallocated on a dynamic disk and then choose New Striped Volume. This starts the New Striped Volume Wizard. Read the Welcome page, and then click Next.
2. Create the volume. The key difference is that you need at least two dynamic disks to create a striped volume.
   After you create a striped volume, you can use the volume just like any other volume. You can't extend a striped set after it's created. Therefore, you should carefully consider the setup before you implement it.

Recovering a Failed Simple, Spanned, or Striped Disk

Simple disks are the easiest to troubleshoot and recover because there is only one disk involved. Spanned or striped disks, on the other hand, have multiple disks and the failure of any one disk makes the entire volume unusable. The drive status might show it is Missing, Failed, Online (Errors), Offline, or Unreadable.

The Missing (and sometimes Offline) status usually happens if drives have been disconnected or powered off. If the drives are part of an external storage device, check the storage device to ensure that it is connected properly and has power. Reconnecting the storage device or turning on the power should make it so the drives can be accessed. You then must start Disk Management and rescan the disks by selecting Rescan Disks from the Action menu. When Disk Management finishes, right-click the drive that was missing, and then choose Reactivate.

The Failed, Online (Errors), and Unreadable statuses indicate input/output (I/O) problems with the drive. As before, try rescanning the drive, and then try to reactivate the drive. If the drive doesn't come back to the Healthy state, you might need to replace it.