1. A verification system for validating data written to logical blocks on a storage subsystem, said storage subsystem being adapted so that during write operations of data to the logical blocks, an additional sequence code is written to each logical block whereby said sequence code remains constant for each write operation batch and whereby said sequence code is incremented for each new write operation batch, said verification system comprising: a data reader for reading respective first and second sequence codes (S(n) and S(n+1)) from consecutive first and second logical blocks (L(n) and L(n+1)); a validity engine for checking validity by applying the following operations: invalidating a corresponding write operation batch if a first sequence code (S(n)) is less than the second sequence code (S(n+1)) and a block offset (F(n+1)) of the second logical block (L(n+1)) is not equal to zero; and invalidating the corresponding write operation batch if the first sequence code S(n) is more than the second sequence code S(n+1) and a block offset (F(n)) of a first logical block (L(n)) does not correspond to a number of logical blocks in a corresponding batch write operation for the first logical block (L(n)); and an error notifier for notifying an error for each invalidated write operation batch.