Apparatus and method of null data skip remote copy
AssigneeHitachi, Ltd.
InventorNaoki Watanabe
Life of this patent
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Abstract
A method and apparatus are provided for enhancing the performance of storage systems is described. In the making of an initial copy to a secondary subsystem, or in the initial storage of data onto a primary storage subsystem, null data is skipped. The data may be skipped by sending the non-null data in sequence so missing addresses are identified as being null data, or a skip message may be used to designate regions where null data is to be present.
Claims21
A method for copying information from a primary storage system to a secondary storage system, the method comprising:
- at the primary storage system, analyzing the information to be copied to determine if it constitutes data desired to be copied or null data which does not need to be copied;
- transmitting to the secondary storage system the data desired to be copied and not transmitting the null data;
- at the secondary storage system, writing to a storage unit in the secondary storage system the information that constitutes the data desired to be copied;
- and
- at the secondary storage system, writing to the storage unit in the secondary storage system a pattern of data other than null data at the location where null data would have been stored had it been transmitted to the secondary storage system.
A method for copying information from a primary storage system to a secondary storage system, the method comprising:
- at the primary storage system, analyzing the information to be copied to determine if it constitutes data desired to be copied or null data which does not need to be copied;
- transmitting to the secondary storage system the data desired to be copied and not transmitting the null data;
- and
- at the secondary storage system, writing to a storage unit in the secondary storage system the information to be copied,
- wherein the step of transmitting further comprises transmitting to the secondary storage system a pattern for the null data to be written onto the secondary storage system at the location where null data would have been stored had it been transmitted to the secondary storage system.
A method for copying information from a primary storage system to a secondary storage system, the method comprising:
- at the primary storage system, analyzing the information to be copied to determine if it constitutes data desired to be copied or null data which does not need to be copied;
- transmitting to the secondary storage system the data desired to be copied and not transmitting the null data;
- at the secondary storage system, writing to a storage unit in the secondary storage system the information to be copied;
- transmitting to the secondary storage system a skip message which indicates that a block of null data is present on the primary storage system and will not be transmitted to the secondary storage system, wherein the skip message further comprises a pattern for data to be written onto the secondary storage system at the location where null data would have been stored had it been transmitted to the secondary storage system.
A method for copying information from a primary storage system to a secondary storage system, the method comprising:
- at the primary storage system, analyzing the information to be copied to determine if it constitutes data desired to be copied or null data which does not need to be copied;
- transmitting to the secondary storage system the data desired to be copied and not transmitting the null data;
- and
- at the secondary storage system, writing to a storage unit in the secondary storage system the information to be copied,
- the data to be copied being transmitted from the primary storage system to the secondary storage system in a sequential order,
- the secondary storage system writing null data onto the storage unit when the secondary storage unit detects gaps in the sequential order.
A method for copying information from a primary storage system to a secondary storage system, the method comprising:
- at the primary storage system, analyzing the information to be copied to determine if it constitutes data desired to be copied or null data which does not need to be copied;
- transmitting to the secondary storage system the data desired to be copied and not transmitting the null data;
- and
- at the secondary storage system, writing to a storage unit in the secondary storage system the information to be copied,
- wherein the analyzing is performed as the information is transmitted on a bus in the primary storage system,
- wherein a DMA controller is used to snoop the bus and analyze the information.
In a system having a host and a storage system coupled to the host, the storage system including a channel controller coupled to the host and apparatus for storing data, a method for writing data into the apparatus comprising:
- monitoring the data as it is transferred to the storage system;
- when a block of data consists only of null data sending a skip message to the apparatus to cause the apparatus not to write that null data and instead writes a pattern of data other than null data;
- and
- when a block of data consists of non-null data sending that data to the apparatus and causing the apparatus to write that data.
In a system having a host and a storage system coupled to the host, the storage system including a channel controller coupled to the host and apparatus for storing data, a method for writing data into the apparatus comprising:
- monitoring the data as it is transferred to the storage system;
- when a block of data consists only of null data sending a skip message to the apparatus to cause the apparatus not to write that null data;
- and
- when a block of data consists of non-null data sending that data to the apparatus and causing the apparatus to write that data,
- wherein the skip message further comprises a pattern for the null data and the address of the null data.
At a primary storage system, a method of selecting stored data to send from the primary storage system to a secondary storage system comprising:
- reading a selected amount of the stored data;
- determining if the stored data is null data or non-null by using a DMA controller snoop a data bus over which data is sent to the secondary storage system;
- if the stored data is non-null data then sending it with a command to the secondary storage system to cause the secondary storage system to store the data;
- if the stored data is null data then not sending it to the secondary storage system;
- and
- repeating the preceding steps until all of the stored data has been either sent to the secondary system or has been determined to be null data.
Dependencies are inferred from the claim text.