Method and apparatus for testing memory devices under load

A method of verifying operation of a new and an untrusted memory device that is added to a computer system having an existing and a trusted memory device when said computer system, including said untrusted memory device and said trusted memory device, is thereafter operated under load, the method comprising the steps of:

• as said computer system operates under load, providing for concurrently shadowing all write operations made to said trusted memory device to said untrusted memory device;
• as said computer system operates under load, providing for responding to a read request by reading requested data from both said trusted memory device and said untrusted memory device;
• providing for comparing said requested data read from said trusted memory device to said requested data read from said untrusted memory device;
• and
• if said data comparing differs, providing for returning said requested data read from said trusted memory device, and generating an error indication.

A method of operating a computing system having a preexisting and trusted memory device after a new and untrusted memory device has been added to said computing system, wherein, as said computing system thereafter operates in a normal load environment, said trusted and untrusted memory devices receive and return the same data values if said untrusted memory device is operating properly, the method comprising the steps of:

• operating said computing system in said normal load environment;
• performing a write operation directed to said trusted memory device by writing data to both said trusted and said untrusted memory device;
• performing a read operation by concurrently reading data from both said trusted and said untrusted memory devices;
• comparing said data read from said trusted and said untrusted memory devices during said performing a read operation step;
• and
• generating an error indication if said data read from said trusted and said untrusted memory devices during said performing a read operation step are not the same data value.

A method of operating a computing system having a preexisting and trusted memory device after a new and untrusted memory device has been added to said computing system, wherein, as said computing system thereafter operates in a normal load environment, said trusted and untrusted memory devices receive and return a same data value if said untrusted memory device is operating properly, the method comprising the steps of:

• operating said computing system in said normal load environment;
• performing a write operation directed to said trusted memory device by writing data to both said trusted and said untrusted memory device;
• and
• performing a background test by reading a predetermined content of each of said trusted and said untrusted memory device, comparing said two read predetermined contents, and generating an error indication if said two read predetermined contents differ.

A computer program product for use in verifying a desired operation of a new and an untrusted memory device that is added to a computer having an existing and a trusted memory device when said computer, including said untrusted memory device and said trusted memory device, is thereafter operated under load, the computer program product comprising a computer usable medium having:

• computer readable program code devices configured to cause a computer operating under load to effect concurrently shadowing all write operations to said trusted memory device to said untrusted memory device;
• computer readable program code devices configured to cause a computer operating under load to effect responding to a read request by reading requested data from both said trusted memory device and said untrusted memory device;
• and
• computer readable program code devices configured to cause a computer operating under load to effect comparing said requested data read from said trusted memory device to said requested data read from said untrusted memory devices;
• and
• computer readable program code devices configured to cause a computer operating under load to effect generating an error indication if said requested data read from said trusted memory device differs from said requested data read from said untrusted memory devices.

In a computer system that contains a preexisting trusted memory device and a new untrusted memory device, apparatus for checking operation of said new untrusted memory device as said computer system, including both said preexisting trusted memory device and said new untrusted memory device, operates in a normal operating environment, comprising:

• a workstation generating read and write requests to said preexisting trusted memory device;
• a shadowing device interposed between said workstation and said preexisting trusted and said new untrusted memory devices;
• said shadowing device operating to concurrently duplicate all read and write operations to said preexisting trusted and said new untrusted memory devices;
• a comparator for comparing data returned from said preexisting trusted memory device to data returned from said new untrusted memory device in response to said read operations, and for generating an error signal if said data returned from said preexisting trusted memory device and said new untrusted memory device differ;
• and
• an error reporter operable to report an error in response to said error signal, and to return said data returned from said preexisting trusted memory device for use in said computer system.