RAID 1 mirror meshed into a co-existing RAID 5 parity stream

1. A computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to perform a method comprising:

storing an operating system in minor stripes on a first data storage device forming a first logical storage unit;

storing data in major stripes across a plurality of data storage devices forming a second logical data storage unit, wherein each major stripe includes a plurality of minor stripes storing data and a parity stripe; and

calculating the parity stripe from the plurality of minor stripes within the major stripe and a corresponding one of the minor stripes on the first data storage device, wherein the minor stripes on the first data storage device match the size of the minor stripes on the array of data storage devices.

2. The computer program product of claim 1 , wherein the parity stripe is distributed across the plurality of data storage devices.

3. The computer program product of claim 1 , wherein there is no data stored on the first data storage device.

4. The computer program product of claim 1 , wherein the operating system is the only software stored on the first data storage device.

5. The computer program product of claim 1 , wherein the first data storage device is a first direct attached storage subsystem of a computer and the array of data storage devices is a second direct attached storage subsystem of the computer.

6. The computer program product of claim 1 , wherein the plurality of data storage devices includes at least three data storage devices.

7. The computer program product of claim 1 , wherein the first data storage device does not contain any parity data for the plurality of data storage device.

8. The computer program product of claim 1 , wherein the computer is able to boot from the operating system on the first data storage device without access to the plurality of data storage devices.

9. The computer program product of claim 1 , wherein the plurality of data storage devices are able to provide access to the data without access to the first data storage device.

10. The computer program product of claim 1 , the method further comprising:

recreating the data stripes and parity stripes stored on an identified one of the plurality of data storage devices using the first data storage device and the data and parity stripes on the other data storage devices in response to failure of the identified data storage device.

11. The computer program product of claim 1 , the method further comprising:

recreating the operating system on a new data storage device using the data and parity stripes on the plurality of data storage devices in response to failure of the first data storage device.

12. The computer program product of claim 1 , the method further comprising:

generating and storing new parity data to be stored in the parity stripes in response to replacing the operating system on the first data storage device.

13. The computer program product of claim 1 , the method further comprising:

generating and storing new parity data to be stored in the parity stripes in response to replacing the first data storage device.