Data Gap Management in a Remote Data Mirroring System

Abstract

A method includes monitoring a sequence of transactions in one or more volumes. The transactions are transferred to a primary storage ( 112 ) in a given order, and are replicated to a secondary storage ( 114 ). The volumes belong to a volume group ( 204 ) for which the transactions are guaranteed to be replicated while retaining the given order. Artificial write transactions ( 228 ) are periodically issued to a protection application field, which is redefined in a given volume ( 212 ) belonging to the volume group. Records indicative of the transactions, including the artificial transactions, are stored in a disaster-proof storage unit ( 144 ). Upon verifying that a given artificial transaction has been successfully replicated in the secondary storage, the records, corresponding to the given artificial write transaction and the transactions that precede it in the sequence are deleted from the disaster-proof storage unit.

1 . A method for data protection, comprising:
 monitoring a sequence of transactions that modify data in one or more volumes, wherein the transactions are transferred from one or more data sources to a primary storage in a given order and are replicated to a secondary storage, and wherein the one or more volumes belong to a volume group for which the transactions are guaranteed to be replicated to the secondary storage while retaining the given order;   periodically issuing artificial write transactions to a protection application field, which is predefined in a given volume belonging to the volume group, so as to insert the artificial write transactions into the sequence;   storing respective records indicative of the transactions of the sequence, including the artificial write transactions, in a disaster-proof storage unit, in order to enable reconstruction of at least part of the data of the volume group using at least a portion of the data that is replicated in the secondary storage device and at least some of the records that are stored in the disaster-proof storage unit upon occurrence of an event that affects data storage in the primary storage; and   upon verifying that a given artificial write transaction has been successfully replicated in the secondary storage, deleting from the disaster-proof storage unit the records corresponding to the given artificial write transaction and the transactions that precede the given artificial write transaction in the sequence.   
     
     
         2 . The method according to  claim 1 , wherein verifying that the given artificial write transaction has been successfully replicated comprises periodically reading the artificial write transactions from the secondary storage. 
     
     
         3 . The method according to  claim 2 , wherein periodically reading the artificial write transactions comprises modifying a period of time between consecutive reading operations of the artificial write transactions in real time. 
     
     
         4 . The method according to  claim 1 , wherein the volume group comprises a consistency group. 
     
     
         5 . The method according to  claim 1 , wherein issuing the artificial write transactions comprises assigning the artificial write transactions respective unique values. 
     
     
         6 . The method according to  claim 5 , wherein the unique values comprise serial indices. 
     
     
         7 . The method according to  claim 5 , wherein the unique values comprise time stamps. 
     
     
         8 . The method according to  claim 5 , wherein verifying that the given artificial write transaction has been successfully replicated comprises reading a unique value of the given artificial write transaction, and verifying that the read unique value is different from a previously-read unique value. 
     
     
         9 . The method according to  claim 1 , wherein periodically issuing the artificial write transactions comprises modifying a period of time between consecutive artificial write transactions in real time. 
     
     
         10 . The method according to  claim 1 , wherein the protection application field is comprised in a dedicated protection application volume that belongs to the volume group. 
     
     
         11 . A data protection apparatus, comprising:
 an interface for monitoring a sequence of transactions that modify data in one or more volumes, wherein the transactions are transferred from one or more data sources to a primary storage in a given order and are replicated to a secondary storage, and wherein the one or more volumes belong to a volume group for which the transactions are guaranteed to be replicated to the secondary storage while retaining the given order; and   a processor, which is configured to periodically issue artificial write transactions to a protection application field that is predefined in a given volume belonging to the volume group so as to insert the artificial write transactions into the sequence, to store respective records indicative of the transactions of the sequence, including the artificial write transactions, in a disaster-proof storage unit, and to delete from the disaster-proof storage unit, upon verifying that a given artificial write transaction has been successfully replicated in the secondary storage, the records corresponding to the given artificial write transaction and the transactions that precede the given artificial write transaction in the sequence.   
     
     
         12 . The apparatus according to  claim 11 , wherein the processor is configured to verify that the given artificial write transaction has been successfully replicated by periodically reading the artificial write transactions from the secondary storage. 
     
     
         13 . The apparatus according to  claim 12 , wherein the processor is configured to modify a period of time between consecutive reading operations of the artificial write transactions in real time. 
     
     
         14 . The apparatus according to  claim 11 , 0wherein the volume group comprises a consistency group. 
     
     
         15 . The apparatus according to  claim 11 , wherein the processor is configured to assign the artificial write transactions respective unique values. 
     
     
         16 . The apparatus according to  claim 15 , wherein the unique values comprise serial indices. 
     
     
         17 . The apparatus according to  claim 15 , wherein the unique values comprise time stamps. 
     
     
         18 . The apparatus according to  claim 15 , wherein the processor is configured to verify that the given artificial write transaction has been successfully replicated by reading a unique value of the given artificial write transaction, and verifying that the read unique value is different from a previously-read unique value. 
     
     
         19 . The apparatus according to  claim 11 , wherein the processor is configured to modify a period of time between consecutive artificial write transactions in real time. 
     
     
         20 . The apparatus according to  claim 11 , wherein the protection application field is comprised in a dedicated protection application volume that belongs to the volume group. 
     
     
         21 . The apparatus according to  claim 11 , wherein the processor is configured to create the protection application field prior to issuing the artificial write transactions. 
     
     
         22 . The apparatus according to  claim 11 , wherein the processor is configured to create a protection application volume, which belongs to the volume group and comprises the protection application field, prior to issuing the artificial write transactions.