Abstract:
A storage system includes a first storage apparatus and a second storage apparatus including a second controller for sequentially transferring a copy of the part of the segments of data from a second buffer into a second storage device segment by segment in the same sequence as the second buffer have received a copy of the part of segments of data from a first buffer of the first storage apparatus. The second controller producing a backup copy in a backup data storage portion by copying a copy of one of the segments of the data stored in the second storage device that has been transferred from the second buffer into the second storage device while transferring a copy of the subsequent segment of the data next to said one of the segments of the data in the sequence from the second buffer to the second storage device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2009-003978, filed on Jan. 9, 2009, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to a storage system, a backup storage apparatus, and a backup control method. 
     BACKGROUND 
     Conventionally, there has been known a Remote Equivalent Copy method (REC) as a function of protecting data from disasters, terrorism attacks, and the like and quickly restoring data. The REC is, specifically, a function of copying data stored in a storage apparatus to another storage apparatus installed in a remote site. 
     Meanwhile, the storage apparatus controls the sequence in which data is written to a disk in such a manner that even if writing to the disk suddenly stops, for example, due to a crash of the sever OS (Operating System), data may be restored to its original state. Such a writing sequence control is also performed in a storage apparatus of a copy destination (hereinafter referred to simply as a “copy destination”) in the same manner when the REC is performed. For this reason, in order for the copy destination to restore data received from a storage apparatus of a copy source (hereinafter referred to simply as a “copy source”) to the same state as that of the copy source, the sequence (transfer sequence) in which data is copied from the copy source to the copy destination is requested to be the same as the sequence in which data is written to the copy source. 
     As the method of guaranteeing the sequence in which data is written to a copy destination, there is a method by which copy data to be transferred to the copy destination is temporarily stored in a buffer and the data in the buffer is collectively transferred to the copy destination in a predetermined timing. 
     There is Japanese Laid-Open Patent Publication No. 2006-260292 as a reference document. 
     SUMMARY 
     According to an aspect of the embodiment, a storage system includes a first storage apparatus for storing data that have been sequentially updated, and a second storage apparatus for storing a copy of the data stored in the first storage apparatus, the first storage apparatus includes a first storage device for storing a plurality of segments of data that have been sequentially updated segment by segment, a first buffer for receiving a copy of the data from the first storage device and sending out the copy of the data to the second storage apparatus, and a first controller for sequentially transferring a copy of a part of the segments of the data from the first storage device into the first buffer segment by segment in the same sequence as the segments of data have been updated in the first storage device and for controlling the first buffer to sequentially sending out the copy of the part of the segments of the data to the second storage apparatus segment by segment in the same sequence as the copy of the segments of data have been transferred to the first buffer, the second storage apparatus includes a second storage device for storing a copy of the segments of the data stored in the first storage apparatus, the second storage device including a backup data storage portion for storing a backup copy of the segments of the data, a second buffer for receiving the copy of the part of the segments of the data from the first buffer of the first storage apparatus and transferring the copy of the part of the segments of the data to the second storage device, and a second controller for sequentially transferring the copy of the part of the segments of the data from the second buffer into the second storage device segment by segment in the same sequence as the second buffer have received the copy of the part of the segments of the data from the first buffer, the second controller producing a backup copy in the backup data storage portion by copying a copy of one of the segments of the data stored in the second storage device that has been transferred from the second buffer into the second storage device while transferring a copy of the subsequent segment of the data next to said one of the segments of the data in the sequence from the second buffer to the second storage device. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates a process flow of a storage system. 
         FIG. 2  is a block diagram illustrating a configuration of the storage system. 
         FIG. 3  illustrates a state in which copy data acquired from the storage apparatus of the copy source is stored in a copy process wait queue. 
         FIG. 4  illustrates a state in which a current receiving buffer is fetched from the copy process wait queue to perform a copy process. 
         FIG. 5  illustrates a state in which current receiving buffers in the copy process wait queue are switched. 
         FIG. 6  illustrates a state in which a plurality of OPCs is simultaneously activated to back up copy data. 
         FIG. 7  is a flowchart illustrating a process procedure of the storage apparatus of the copy source. 
         FIG. 8  is a flowchart illustrating a process procedure of a CM provided in the storage apparatus of the copy destination. 
         FIG. 9  illustrates a computer executing backup programs. 
         FIG. 10A  illustrates a state in which data is written to a copy source volume. 
         FIG. 10B  illustrates a state in which the copy source creates a bitmap as the data is written. 
         FIG. 10C  illustrates a state in which data writing sequentiality is not guaranteed. 
         FIG. 11A  illustrates a state in which data written to the copy source volume is stored in a buffer. 
         FIG. 11B  illustrates a state in which data is stored in the copy destination volume. 
         FIG. 12  illustrates a state in which copy data is transferred from the copy source to two volumes of the copy destination. 
         FIG. 13  illustrates a state in which a remote copy is suspended when dual backups of data are performed in the copy destination. 
         FIG. 14  illustrates a case in which the copy source volume fails while a remote copy using REC is being suspended. 
         FIG. 15A  illustrates a state in which data is written to the copy source while the remote copy using REC is being suspended. 
         FIG. 15B  illustrates a state in which when the remote copy is resumed, update data is backed up to the copy destination in a sequence different from the sequence in which data is written to the copy source. 
         FIG. 16  illustrates a state in which a copy process of data stored in buffers to the copy destination volume is not synchronized with an activation of the OPC. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, by referring to accompanying drawings, embodiments in accordance with a backup control apparatus, a storage system, a backup control program, and a backup control method disclosed in the present technique will be described in detail. 
     First, the storage system in accordance with the comparison embodiment will be described by referring to drawings. 
     Hereinafter, a data transfer method will be specifically described by comparing a case in which the sequence in which data is written to a copy destination is not guaranteed. First, the case in which the sequentiality is not guaranteed will be described by referring to  FIGS. 10A to 10C .  FIG. 10A  illustrates a state in which data is written to a copy source volume;  FIG. 10B  illustrates a state in which the copy source creates a bitmap as the data is written; and  FIG. 10C  illustrates a state in which the sequence in which data is written to the copy source does not match the sequence in which data is backed up to the copy destination. 
     While the REC is being activated, as illustrated in  FIG. 10A , a session is established between a copy source volume  700  and a copy destination volume  800 . At this time, when an instruction to write data A to a region  700   a  of the copy source volume  700  and an instruction to write data B to a region  700   b  thereof are received, the copy source writes the data A and B to the region  700   a  and the region  700   b  respectively as illustrated in  FIG. 10B . Then, the copy source creates a bitmap  750  indicating which region of the volume  700  is updated. Specifically, the copy source sets “1” or “0” to each of the regions  750   a  to  750   c  of the bitmap  750  in such a manner that “1” is set to the values of the regions  750   a  and  750   b  corresponding to the respective regions  700   a  and  700   b  of the volume  700  where data is updated, and “0” is set to the value of the region  750   c  corresponding to the region  700   c  of the volume  700  where data is not updated. 
     Then, the copy source transfers the updated data to the copy destination. Specifically, the copy source refers to each of the regions  750   a  to  750   c  of the bitmap  750  to determine in which region of the volume  700 , data is updated, and transfers only the data stored in the updated region to the copy destination. However, the copy method using the bitmap  750  may not control the sequence in which these updates occur when data is updated in a plurality of regions of the volume  700 . For this reason, the copy source checks each of the regions  750   a  to  750   c  of the bitmap  750  to find a region (having a value of “1”) where data is updated, and each time the region is found, the copy source transfers the data stored in the region of the volume  700  corresponding to the region to the copy destination. 
     By performing such a process, the copy source may determine that data is updated in the sequence from data B to data A although the data is written in the sequence from data A to data B. In that case, as illustrated in  FIG. 10C , the copy source transfers data in the sequence from data B to data A. Therefore, data is written in the sequence from data B to data A in a copy destination volume  800 . As a result, the data sequentiality may not be maintained between the copy source and the copy destination. Accordingly, it is difficult to execute a restore using the data stored in the copy destination. 
     Alternatively, there is a method by which a buffer is used to guarantee the sequence of writing data to the copy source before transferring data. Hereinafter, such a data transfer method will be described.  FIG. 11A  illustrates a state in which data written to the copy source volume is stored in a buffer; and  FIG. 11B  illustrates a state in which data which the copy destination receives from the copy source and stores in the buffer is stored in the copy destination volume. 
     As illustrated in  FIG. 11A , when data A and data B are written to the sequence from data A to data B in the copy source volume  700 , the copy source stores data A and data B in buffer segments  770   a  and  770   b  respectively in the same written sequence. Then, when these buffer segments  770   a  and  770   b  (hereinafter referred to simply as “buffers  770   a  and  770   b ”) become full or a specific time has elapsed since storing of data started, the copy source transfers data stored in these buffers  770   a  and  770   b  to the copy destination collectively in units of buffers. 
     Then, as illustrated in  FIG. 11B , when data is received from the copy source in units of buffers, the copy destination stores the data in buffer segments  870   a  and  870   b  (hereinafter referred to simply as “buffers  870   a  and  870   b ”) in the received sequence. Then, the copy destination transfers the data to the volume  800  in the sequence from buffer  870   a  to buffer  870   b  and stores the data in the volume  800 . This method allows the copy destination to always write the data received from the copy source to its own volume  800  in the same sequence as the data was written to the copy source. 
     Further, in recent years, in order to protect data more reliably, dual backups may sometimes be performed on copy source data. At this time, as illustrated in  FIG. 12 , the copy source volume  700  transfers the update data to buffers  870   a ,  870   b ,  970   a , and  970   b  through the buffers  770   a  and  770   b , and the update data A and B are stored in two volumes (volume A  800  and volume B  900 ) of the copy destination. This method gives a large load to the communication line and thus may reduce data transfer efficiency. In light of this, such reduction of transfer efficiency may be prevented by backing up data acquired from the copy source in the copy destination. 
     As one of the backup methods by which dual backups are performed in the copy destination as described above, there may be considered a method in which dual backups are performed in the copy destination by temporarily suspending the REC from the copy source to the copy destination. 
     More specifically, when the update data of the copy source is backed up to two volumes of the copy destination, as illustrated in  FIG. 13 , the copy destination first stores the data A and data B transmitted in units of buffers, in regions  800   a  and  800   b  each corresponding to the data A and B in the volume A  800 . Then, the copy destination backs up the data A and data B stored in the volume A  800  to another volume B  900  which is also provided in the copy destination using an One Point Copy method (OPC). The OPC is a method of generating replicated data (snapshot) at a predetermined point of time of the data to be backed up when a backup is performed. However, if the REC is suspended, following problems may occur. 
     For example, assume that as illustrated in  FIG. 14 , while a remote copy using REC is being suspended, data C is newly written to a region  700   a  of the copy source volume  700 , and subsequently the copy source volume  700  fails due to an earthquake or the like. In this case, the data C is not transferred to the copy destination because the REC is suspended. Accordingly, if the copy source volume  700  fails while the remote copy using REC is being suspended, data that has been written from when REC was suspended to when the copy source volume failed is lost, and thus it may be difficult to restore the data. 
     Alternatively, when data C and data D are written to the volume  700  while the remote copy using REC is being suspended, the copy source controls these writes using a bitmap  750  instead of recording buffers as illustrated in  FIG. 15A . Then, when the remote copy is resumed, the copy source checks the bitmap  750  and stores the data C and data D in buffers  770   a  and  770   b  respectively in the sequence determined to be updated. For this reason, as illustrated in  FIG. 15B , there may occur a case where the sequence in which data C and data D are written to the volume  700  does not match the sequence in which data C and data D are transferred to the copy destination. 
     As described above, it is not preferable in operation to suspend the remote copy using REC. Therefore, it is preferable not to suspend the remote copy when dual backups are to be performed in the copy destination. However, when dual backups are to be performed without suspending the remote copy, the aforementioned data transfer method may not synchronize between the copy process of transferring data stored in the buffer  870  to the volume A  800  and the process of backing up data stored in the volume A  800  to the volume B  900  in the copy destination. Accordingly, backup data may be meaningless. 
     More specifically, assume that data A stored in the buffer  770   a  contains a plurality of pieces of data A 1  to A 3  and data B stored in the buffer  770   b  contains a plurality of pieces of data B 1  to B 3  as well. When these pieces of data A 1  to A 3  and data B 1  to B 3  are received in units of buffer segments, the copy destination performs a copy process to the copy destination volume A  800  in units of buffer segments. At this time, when a backup by OPC is activated, the copy destination backs up data stored in the volume A  800  regardless of the copy process from the buffer  870  to the copy destination volume A  800 . That is, the copy destination may perform a backup process to the volume B  900  before the copy process of the data A 1  and data A 2  is not completed. In this case, as illustrated in  FIG. 16 , before update data A 1  and data A 2  are stored in the volume A  800 , currently stored data (data A 1  (OLD) and data A 2  (OLD)) are stored in the volume B  900  as the update data, and thus the backup data may be meaningless. 
     Therefore, optimization of the backup process when dual backups are performed on the copy data acquired from the copy source in the copy destination is demanded. 
     Hereinafter, the outline of the storage system in accordance with the present embodiment will be described by referring to drawings.  FIG. 1  explains a process flow of the storage system in accordance with the present embodiment. The storage system in accordance with the present embodiment copies data stored in a storage apparatus of a copy source to a storage apparatus of a copy destination through a communication path as well as performs dual backups of data acquired from the storage apparatus of the copy source in the storage apparatus of the copy destination. 
     Here, the storage system in accordance with the present embodiment performs a remote copy using REC as a method of copying data from a storage apparatus of the copy source (hereinafter referred to simply as “copy source”) to a storage apparatus of the copy destination (hereinafter referred to simply as “copy destination”). The REC is a method of copying data stored in a storage apparatus to another storage apparatus installed in a remote site. 
     Specifically, as illustrated in  FIG. 1 , during REC execution, for example, when an instruction to write data A and data B is acquired, the copy source writes data to a copy source volume  70 . At this time, the copy source memorizes which region of data is updated in what sequence. 
     When the process of writing this data is completed, the copy source reads the data updated by the writing process from the copy source volume  70 , and then stores this data in a sending buffer  77  in the update sequence. More specifically, when data is written to the copy source volume  70  in the sequence from data A to data B, the copy source first stores data A in a sending buffer segment A  77   a  (hereinafter referred to simply as “buffer  77   a ”). At this time, data A contains data A 1  to A 3 . 
     Then, when the sending buffer A  77   a  becomes full or a specific time has elapsed since the first storing started, the copy source stops storing data in the sending buffer A  77   a , and fixes a block of data to be copied to the copy destination. Then, the copy source switches to another sending buffer segment B  77   b  (hereinafter referred to simply as “buffer  77   b ”) to resume storing. More specifically, when the sending buffer A becomes full by storing data A 1  to A 3 , the copy source switches the sending buffers  77  from the sending buffer A  77   a  to the sending buffer B  77   b  and starts storing next data or data B. Note that at this time, data B contains data B 1  to B 3 . 
     The copy destination acquires data (hereinafter referred to simply as “copy data”) transferred from the copy source through a communication path. Then, the copy destination stores the acquired copy data in a receiving buffer  87  in the acquired sequence. More specifically, when copy data is acquired from the copy source in the sequence from data A to data B, the copy destination stores these pieces of data in the receiving buffer  87  in the sequence from data A to data B. Next, the copy destination transfers the copy data stored in the receiving buffer  87  to a copy destination volume A  80  in the stored sequence. More specifically, the copy destination first transfers data A 1  to A 3  stored in the receiving buffer A  87   a  to the copy destination volume A  80 . Then, when this copy process is completed, the copy destination switches to another receiving buffer or a receiving buffer B  87   b  and transfers data B 1  to B 3  to the copy destination volume A  80 . Note that hereinafter copy data stored in the receiving buffer  87  may be referred as buffer data. 
     Further, the copy destination backs up the copy data stored in the copy destination volume. Specifically, the copy destination performs a backup process using OPC. The OPC is a process of generating replicated data (snapshot) at a predetermined point of time of the data to be backed up when a backup is performed. That is, according to the present embodiment, the copy destination generates a snapshot of the data stored in the copy destination volume A  80  in a copy destination volume B  90 . 
     Here, according to the present embodiment, the backup process to the copy destination volume B  90  is performed after the copy process of transferring the buffer data from the receiving buffer A  87   a  to the copy destination volume A  80  is completed and during the process of switching to a next receiving buffer B  87   b . That is, the copy destination completes transferring all the data A 1  to A 3  stored in the receiving buffer A  87   a  to the copy destination volume A  80 , and then activates the OPC as well as switches to another receiving buffer or a receiving buffer B  87   b . As described above, the backup process using OPC is performed during the process of switching the receiving buffers. 
     In this manner, the storage system in accordance with the present embodiment synchronizes between the copy process of transferring copy data to the copy destination volume A  80  and the process of backing up the copy data to the copy destination volume B  90 . This method of performing a backup process during the copy process of transferring copy data may prevent a situation where the data backed up in the copy destination volume B  90  does not match the data stored in the copy destination volume A  80 . 
     Next, the configuration of the storage system in accordance with the present embodiment will be specifically described by referring to drawings.  FIG. 2  is a block diagram illustrating the configuration of the storage system in accordance with the present embodiment. As illustrated in  FIG. 2 , the storage system S in accordance with the present embodiment includes a host apparatus  1 , a copy source storage apparatus  2  (copy source  2 ), and a copy destination storage apparatus  3  (copy destination  3 ). The copy source  2  is mutually connected to the copy destination  3  through a network  4  serving as a communication path. A remote copy using REC is performed through this network  4 . Examples of the network  4  include the Internet, LAN, WAN, and the like. 
     The host apparatus  1  is a device used by an operator, for example, corresponding to a computer terminal used by a user who manages the copy source  2 . The copy source  2  includes a CA (Channel Adapter)  21 , an RA (Remote Adapter)  22 , a CM (Centralized Module)  23 , and a copy source volume  24 . 
     The CA  21  serves as an interface (I/F) control portion to and from the host apparatus  1  and controls sending and receiving information to and from the host apparatus  1 . The copy source  2  uses this CA  21  acquires not only an instruction to write data, but also other instructions to execute a remote copy using REC, a backup by OPC, and the like. The RA  22  serves as an interface (I/F) control portion to and from the copy destination  3  and controls transferring copy data to and from the copy destination  3 . 
     Examples of the copy source volume  24  include an HDD (Hard Disk Drive), an MO disk (Magneto Optical Disk) and other disk devices to store various kinds of data therein. This copy source volume  24  corresponds to a data storage unit. It is noted that the copy source volume  24  may be any device as long as the device may store data, and is not limited to a disk device. 
     The CM  23  mainly serves as a processing portion executing a REC remote copy process and includes a control portion  210 , a storage portion  220 , and a DA (Disk Adapter)  230 . The storage portion  220  serves as a cache or the like and includes a sending buffer region  221  which includes a plurality of sending buffer segments  222   a , 222   b  and  222   c  (hereinafter referred to simply as “buffers  222   a , 222   b  and  222   c ”). The sending buffers  222   a  to  222   c  are a storage region in which data to be transferred to the copy destination  3  is temporarily stored. The DA  230  serves as an I/F control portion to and from the copy source volume  24 , and is used when data is written to the copy source volume  24  in response to a write instruction from the host apparatus  1  or the written data is stored in one of the sending buffers  222   a  to  222   c.    
     The control portion  210  controls the entire copy source  2 . This control portion  210  includes a sending data storage portion  211  and a sending portion  212 . The sending data storage portion  211  functions as a sending data storage unit, and stores data updated by data writing process or the like by the host apparatus  1  of the data stored in the copy source volume  24 , in one of the sending buffers  222   a  to  222   c  in the update sequence. The sending portion  212  functions as a sending unit, and sends the data stored in the sending buffers  222   a  to  222   c  by the sending data storage portion  211  to the copy destination  3  through the network  4  in the update sequence. 
     The copy destination  3  includes an RA (Remote Adapter)  31 , a CA (Channel Adapter)  32 , a CM (Centralized Module)  33 , and copy destination volumes  34   a  and  34   b . The RA  31  serves as an I/F control portion to and from the copy source  2  and controls receiving copy data from the copy source  2 . The CA  32  serves as an I/F control portion to and from the host apparatus  1  and controls sending and receiving information to and from the host apparatus  1 . It is noted that the copy destination  3  may be connected to the host apparatus  1  through the network  4  or other communication path. 
     Examples of the copy destination volumes  34   a  and  34   b  include an HDD (Hard Disk Drive), an MO disk (Magneto Optical Disk) and other disk devices to store various kinds of data therein. It is noted that the copy destination volumes  34   a  and  34   b  may be any device as long as the device may store data, and is not limited to a disk device. According to the present embodiment, the copy destination volume  34   a  corresponds to a copy data storage unit and stores copy data transferred from the copy source  2 . In addition, the copy destination volume  34   b  corresponds to a backup data storage unit and stores backup data of the copy data stored in the copy destination volume  34   a.    
     The CM  33  mainly serves as a processing portion executing a copy process and a backup process, and corresponds to a backup control apparatus. This CM  33  includes a control portion  310 , a storage portion  320 , and DAs (Disk Adapters)  330   a  and  330   b . The storage portion  320  serves as a cache or the like. This storage portion  320  has a copy process wait queue  321 . This copy process wait queue  321  includes a plurality of receiving buffer segments  322   a    322   b  and  322   c  (hereinafter referred to simply as “buffer  322   a ,  322   b  and  322   c ”). The receiving buffers  322   a  to  322   c  are a storage region in which copy data received from the copy source  2  is temporarily stored. The DAs  330   a  and  330   b  each serve as an I/F control portion to and from the copy destination volume A  34   a  and the copy destination volume B  34   b  respectively. 
     The control portion  310  controls the entire copy destination  3 . This control portion  310  includes an acquisition portion  311 , a received data storage portion  312 , a copy process portion  313 , and a backup portion  314 . The acquisition portion  311  functions as an acquisition unit and acquires copy data transferred from the copy source  2  through the network  4  and the RA  31 . 
     The received data storage portion  312  functions as a received data storage unit and stores the copy data acquired from the acquisition portion  311  in the receiving buffers  322   a  to  322   c . Here, the process of storing copy data by this received data storage portion  312  will be described by referring to another drawing.  FIG. 3  illustrates a state in which copy data acquired from the storage apparatus of the copy source is stored in the copy process wait queue. 
     The received data storage portion  312  stores copy data acquired from the copy source  2  in the receiving buffers  322   a  to  322   c  in the acquired sequence. Specifically, as illustrated in  FIG. 3 , when the acquisition portion  311  acquires data stored in the sending buffer A  222   a , the received data storage portion  312  stores the acquired copy data in the first receiving buffer A  322   a  in the copy process wait queue  321 . Then, when the acquisition portion  311  acquires data stored in the sending buffer B  222   b , the received data storage portion  312  stores data stored in the sending buffer B  222   b  in a next receiving buffer B  322   b  in the copy process wait queue  321 . Then, when the acquisition portion  311  acquires data stored in the sending buffer C  222   c , the received data storage portion  312  stores the acquired copy data in a next receiving buffer C  322   c  in the copy process wait queue  321 . 
     The copy process portion  313  functions as a copy process unit, fetches (selects) one of the receiving buffers  322   a  to  322   c  in a sequence in which copy data was stored, and transfers the buffer data stored in the fetched receiving buffer  322  to the copy destination volume A  34   a . Here, the copy process of transferring from the receiving buffer to the copy destination volume A  34   a  by the copy process portion  313  will be described by referring to other drawings.  FIG. 4  illustrates a state in which a current receiving buffer  322   a  is fetched from the copy process wait queue  321  to perform an expansion process.  FIG. 5  illustrates a state in which current receiving buffers  322   b  in the buffer copy process wait queue  321  are switched. 
     When the copy process is performed, the copy process portion  313  first fetches the first receiving buffer A  322   a  from within the receiving buffers  322   a  to  322   c  in the copy process wait queue  321  as a buffer (current buffer) to be executed. Then, the copy process portion  313  transfers copy data (buffer data) A 1  to A 3  stored in the receiving buffer  322   a  to the copy destination volume A  34   a.    
     When the copy process of transferring copy data A to the copy destination volume A  34   a  is completed, the copy process portion  313  switches from the already-executed receiving buffer A  322   a  to a next-to-be-executed receiving buffer B  322   b . More specifically, the process of transferring copy data A to the copy destination volume A  34   a  is completed, the copy process portion  313  fetches a next receiving buffer  322   b  as the current receiving buffer and transfers the buffer data stored in the receiving buffer  322   b  to the copy destination volume A  34   a . Then, as illustrated in  FIG. 5 , the current receiving buffer switches from the receiving buffer A  322   a  to the receiving buffer B  322   b.    
     As described above, the storage system S in accordance with the present embodiment performs a remote copy using the sending buffers and the receiving buffers between the copy source  2  and the copy destination  3  as the REC function and thereby may copy the data stored in the copy source  2  to the copy destination  3  by guaranteeing sequentiality. 
     The backup portion  314  functions as a backup unit, and backs up the buffer data stored to the copy destination volume A  34   a  to the copy destination volume  34   b . In particular, according to the present embodiment, the backup portion  314  performs this backup process after the copy process portion  313  transfers all the buffer data stored in the receiving buffers to the copy destination volume A  34   a . Note that when the copy process of the buffer data is completed, the copy process portion  313  switches to the buffer data stored in a next receiving buffer  322   b  independently of the backup process by the backup portion  314 . 
     That is, when the process of transferring the data from the receiving buffer A  322   a  to the copy destination volume A  34   a  is completed, the backup portion  314  activates OPC. Thereby, the data (i.e., buffer data A 1  to A 3  stored in the receiving buffer A  322   a ) stored in the copy destination volume A  34   a  is backed up to the copy destination volume B  34   b . Note that during this backup process, the process of switching to a next receiving buffer B  322   b  by the copy process portion  313  is performed in parallel. 
     Here, if the buffer data stored in the copy destination volume contains data each stored in a plurality of physical volumes in the copy source  2 , the backup portion  314  executes a backup process on the buffer data for each of the plurality of copy destination volumes corresponding to the plurality of physical volumes. Alternatively, if the buffer data stored in the copy destination volume contains data each stored in a plurality of logical volumes allocated to one physical volume in the copy source  2 , the backup portion  314  executes a backup process on the buffer data for each logical volume allocated to the copy destination volume corresponding to the plurality of logical volumes. Hereinafter, such a process will be described by referring to another drawing.  FIG. 6  illustrates a state in which a plurality of OPCs is simultaneously activated to back up copy data. 
     That is, for example, as illustrated in  FIG. 6 , assume that the copy source  2  has two copy source volumes  24   a  and  24   b  as the physical volume, and two logical volumes  25   a  and  25   b  are allocated to the copy source volume  24   a . Then, assume that the host apparatus  1  writes data A 1  to the logical volume  25   a  of the copy source volume  24   a , and writes data A 2  to the logical volume  25   b  thereof. 
     In such a case, when copy data A 1  to A 3  are acquired from the copy source, the copy process portion  313  stores these pieces of copy data A 1  to A 3  to a volume corresponding in the volume in which these pieces of copy data A 1  to A 3  are stored in the copy source  2 . Specifically, the copy process portion  313  stores data A 1  in a logical volume  35   a  corresponding to the logical volume  25   a  in which data A 1  is stored. In addition, the copy process portion  313  stores data A 2  to a logical volume  35   b  corresponding to the logical volume  25   b  in which data A 2  is stored. Likewise, the copy process portion  313  stores data A 3  to a copy destination volume  34   b  corresponding to the copy source volume  24   b  in which data A 3  is stored. 
     Then, the backup portion  314  simultaneously executes backup processes on the copy data A 1  to A 3  stored in the logical volumes  35   a  and  35   b  and the copy destination volume  34   b . More specifically, the backup portion  314  simultaneously executes an activation of OPC for backing up copy data A 1  to the logical volume  35   c , an activation of OPC for backing up copy data A 2  to the logical volume  35   d , and an activation of OPC for backing up copy data A 3  to the copy destination volume D  34   d . Note that the logical volume  35   c  of the copy destination volume C  34   c  corresponds to the logical volume  35   a  of the copy destination volume A  34   a , the logical volume  35   d  of the copy destination volume C  34   c  corresponds to the logical volume  35   b  of the copy destination volume A  34   a , and the copy destination volume D  34   d  corresponds to the copy destination volume B  34   b.    
     In this manner, according to the present embodiment, when data stored in a plurality of logical volumes allocated to one physical volume in the copy source  2  or data stored in a plurality of physical volumes in the copy source  2  is to be backed up, the backup processes are duplicatedly performed on these pieces of data. This method may reduce the time used for a backup process of copy data stored in one of the receiving buffers  322   a  to  322   c . It is noted that according to the present embodiment, the timing of starting these backup processes (timing of activating OPC) is described as “simultaneous”, but the timing is not necessarily simultaneous, but OPC may be executed in such a timing as each backup process is executed by multiplex. Note that the time used for the backup processes may be minimized by simultaneously activating OPCs. 
     Next, a specific operation of the copy source  2  in accordance with the present embodiment will be specifically described by referring to another drawing.  FIG. 7  is a flowchart illustrating a process procedure of the storage apparatus  2  of the copy source in accordance with the present embodiment. Note that the following process focuses only on the data remote copy using REC of the various operations executed by the copy source  2 . 
     As illustrated in  FIG. 7 , when an instruction to write data is received from the host apparatus  1 , the control portion  210  of the copy source  2  writes data to the copy source volume  24  based on the write instruction (Operation S 101 ). At this time, the control portion  210  stores, in a predetermined region of the storage portion  220 , the information indicating that the data stored in which region of the copy source volume  24  is updated in what sequence. Then, the sending data storage portion  211  reads the data updated by the write process in Operation S 101  from the copy source volume, and stores the data in one of the sending buffers  222   a  to  222   c  in the update sequence (Operation S 102 ). 
     Then, the control portion  210  determines whether or not the sending buffer becomes full or a specific time has elapsed since the first storing started (Operation S 103 ). In this process, if the sending buffer is not full and a specific time has not elapsed since the first storing started (Operation S 103 : No), the control portion  210  returns the process to Operation S 102 . Meanwhile, if a determination is made that the sending buffer becomes full or a specific time has elapsed since the first storing started (Operation S 103 : Yes), the sending data storage portion  211  stops storing data in the sending buffer and fixes a block of data to be copied to the copy destination, and proceeds the process to Operation S 104 . Then, in Operation S 104 , the sending portion  212  sends the update data stored in the sending buffer to the copy source  3  through the RA  22  and the network  4  (Operation S 104 ). 
     Then, a specific operation of the copy destination in accordance with the present embodiment will be specifically described by referring to another drawing.  FIG. 8  is a flowchart illustrating a process procedure of a CM  33  provided in the storage apparatus  3  of the copy destination in accordance with the present embodiment. Note that the following process focuses only on the process of transferring from the receiving buffers  322   a  to  322   c  and backing up copy data of the various operations executed by the copy destination  3 . 
     As illustrated in  FIG. 8 , the acquisition portion  311  acquires the update data (i.e., copy data) transferred from the copy source through the network  4  and RA  31  (Operation S 201 ). Then, the received data storage portion  312  stores the copy data acquired by the acquired sequence in the receiving buffers  322  (Operation S 202 ). 
     Then, the copy process portion  313  transfers the copy data stored in one of the receiving buffers  322   a  to  322   c  to the copy destination volume A  34   a  in the stored sequence (Operation S 203 ). Then, the copy process portion  313  determines whether or not the copy process in Operation S 203  is completed (Operation S 204 ). If a determination is made in this process that the copy process is completed (Operation S 204 : Yes), the backup portion  314  backs up the copy data stored in the copy destination volume A to the copy destination volume B (Operation S 205 ). 
     In addition, after the backup process in Operation S 205  starts, the copy process portion  313  determines whether or not another receiving buffer storing copy data is present in the copy process wait queue  321  (Operation S 206 ). If a determination is made in this process that there is another receiving buffer (Operation S 206 : Yes), the copy process portion  313  switches to a next receiving buffer in the copy process wait queue  321  (Operation S 207 ). When this process is completed, the CM  33  returns the process to Operation S 203  and starts the process of transferring from the receiving buffer switched in Operation S 207 . 
     As described above, according to the storage system in accordance with the present embodiment, the copy process of transferring copy data to the copy destination volume A  34   a  by the copy process portion  313  is synchronized with the backup process of backing up copy data to the copy destination volume B  34   b  by the backup portion  314 . This method may perform a backup process by guaranteeing sequentiality of the backup data without suspending the remote copy using REC when dual backups are performed on the copy data acquired from the copy source  2  in the copy destination  3 . 
     Moreover, according to the storage system in accordance with the present embodiment, the backup process of backing up copy data by the backup portion  314  is performed between after the copy process of transferring from a receiving buffer  322  by the copy process portion  313  completes and before the copy process of transferring from a next receiving buffer  322  starts. This method may guarantee the sequentiality of the backup data and may optimize the timing of starting the backup process. 
     Meanwhile, the various processes described in the above embodiments may also be implemented by causing a computer to execute preliminarily prepared programs. In light of this, hereinafter, by referring to  FIG. 9 , an example of a computer executing backup programs having the same functions as the CM  33  in the copy destination  3  illustrated in the above embodiments will be described.  FIG. 9  illustrates a computer executing the backup programs. 
     As illustrated in  FIG. 9 , a computer  600  serving as the CM  33  is configured to include an HDD  610 , a CPU  620 , a ROM  630  and a RAM  640  which are connected through a bus  650 . 
     The ROM  630  preliminarily stores backup programs exerting the same functions as those in the above embodiments, that is, an acquisition program  631 , a received data storage program  632 , a copy process program  633 , and a backup process program  634  as illustrated in  FIG. 9 . 
     When the CPU  620  reads these programs  631  to  634  from the ROM  630  and executes them, each of the programs  631  to  634  functions as an acquisition process  621 , a received data storage process  622 , a copy process  623 , and a backup process  624  respectively. In this manner, the CPU  620  corresponds to the CM  33  illustrated in  FIG. 2 . 
     Note that the HDD  610  stores various kinds of data to be used by the processes  621  to  624 . The CPU  620  reads various kinds of data stored in the HDD  610  and stores them in the RAM  640 . The processes  621  to  624  use the various kinds of data stored in the RAM  640  to execute various processes such as a backup process. 
     The storage system, the backup storage apparatus and method disclosed in the present embodiment may optimize the backup process when dual backups are performed on the copy data acquired from the copy source in the copy destination. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.