be specified using additional data if desired field 54 in the management table 50 shown in fig2 identifies the time period when data verification or checking is to be triggered the field 55 u201c current sleeping time u201d will have the duration since the responding pair has been powered off this field is valid only when the current mode field 53 is u201c 1 u201d the field u201c data verification option u201d specifies whether data verification operations are to be performed preferably a u201c 0 u201d in field 56 means data verification will not be performed while a u201c 1 u201d means that data verification will be performed in an intermittent sequence for the corresponding disk pair the u201c divided sequence u201d indicates the portion of the disk drive upon which data is to be verified during a given operation for example a cylinder the specific unit of verification is encoded within field 57 in field 57 a u201c 0 u201d can be used to designate a logical cylinder and a u201c 1 u201d may be used to designate eight cylinders the specific units will depend upon the particular implementation chosen the field u201c last checked address u201d 58 is used to identify the address of the portion of the disk pair that was checked in the latest data verification operation each time a data verification operation is performed this field is updated the u201c idle condition u201d field 59 a identifies the status of the pair while it is idle in other words designating whether the pair in operation is in normal mode but not processing i o requests as above the particular usage of this field will depend on the particular implementation in the preferred embodiment the final field u201c power.