JP4921013B2 - Mail server backup system, mail server backup method, program, and recording medium - Google Patents

Description

  The present invention relates to a mail server backup system, a mail server backup method, a program, and a recording medium, and in particular, between the active system and the remote backup environment, identification information such as mail data and a mail identifier accompanying the mail data, Regarding update information such as email deletion etc., it is related to a mail server backup system etc. that enables service continuation in a remote backup environment even if a disaster such as a big earthquake occurs by performing the update information asynchronously while guaranteeing the order of the update information It is.

  Generally, when building a backup environment in the event that the system becomes unavailable due to a disaster such as an earthquake, it is necessary to install a backup system in a remote location that is not affected by the disaster. It is desirable to be able to continue service from this state. For this purpose, it is necessary to replicate the data of the operational server to the backup server, and the electronic mail server is required to replicate mail data such as a mailbox.

  As one of the mail data replication methods, the data stored in a storage device (hard disk or the like) in which the mail data is stored is converted into an operational server by using a disk device or a data mirror function of an OS (Operating System) or a file system. A method of replicating (synchronizing) between the server and the backup server is conceivable (for example, see Patent Document 1).

  Here, the data in the storage device is completely synchronized, so that the active server and the backup server always operate in the same manner on the mail protocol (POP (Post Office Protocol) / IMAP (Internet Message Access Protocol)). Even if you start using, email clients can continue to use without problems.

  However, the data replication method of the storage device has the following problems. The first problem is that a dedicated hardware device having a data mirror function is generally expensive and expensive. On the other hand, the OS or file system data mirror function has a high processing load and is often inferior to dedicated hardware in reliability.

  As a second problem, since it is necessary to guarantee the order of a large amount of disk I / O (Input / Output), a network bandwidth of 100 Mbyte / sec or more is generally used between the operation system and the backup system. It is a point that needs to be secured between. A third problem is that the replication status can be grasped only in units of disk I / O, and the replication status in units of mail is not recorded. For this reason, when a failure (disaster) occurs, it is not possible to determine which email has been copied.

  On the other hand, as a method of not performing data replication of the storage device, a method of performing mail transfer to the backup environment by SMTP (Simple Mail Transfer Protocol) can be considered. In this method, the data transfer amount is small compared to data replication of the storage device, and it is considered that it can be realized in a band of about several M to several tens of Mbyte / sec. Therefore, it is easy to construct a backup environment in a remote place, The server load is also considered to be small.

  However, SMTP replication has the following problems. First, mail meta information (such as UID (Unique Identifier) and READ flag for POP / IMAP protocol) is not duplicated. Second, update information such as e-mail deletion cannot be duplicated. In particular, due to the second problem, the user (mail client) is forced to receive all mail again even after switching the operating system (after starting to use the backup environment).

Incidentally, for example, Patent Document 2 discloses a backup system for a mail server that enables more efficient backup execution by performing information storage processing in units of mailboxes. Patent Document 3 proposes a method of synchronizing data using a synchronization engine including a database that supports tracking, filtering, and recovery synchronization of changed data.
JP 2005-18736 A JP 2002-351719 A JP-A-2005-322250

  As described above, backup using a dedicated hardware device equipped with a data mirror function is costly, it is not easy to secure the implementation environment (wide network bandwidth), and the replication status as a mail server can be grasped. The problem is that it is difficult. In addition, since backup using SMTP mail transfer does not copy mail meta-information or update information, there is a problem in that all mail must be received again by the user (mail client) after switching.

  Therefore, in the present invention, by copying mail data including mail identification information and mail update information for each mail by software, it becomes possible to continue service in an equivalent state between the active system and the remote backup environment. The purpose is to provide a mail server backup system.

  In order to achieve such an object, the present invention provides a mail server for holding mail received from a mail client or mail delivery server in a mailbox, mail stored in the mailbox, and information related to the mail as backup data. A mail server backup system comprising a backup server held as a mail server, wherein the mail server is used for duplication including mail held in the mailbox and information related to the mail in a process of holding the mail A mail data file is created for each mail, and the copy mail data file is transmitted to the backup server. The backup server reads the copy mail data file transmitted from the mail server, and the mail box Characterized by duplicating the information about the stored mail and the e-mail.

  The present invention is a mail server backup system composed of a mail server and a backup server, and realizes duplication including mail identification information and mail update information for each mail by software. The target of backup is mail data including a mail body and information related to mail such as a mail UID and a mail deletion instruction, and data for duplication of the mail data is created for each mail by a mail server. The created mail data for duplication is transmitted from the mail server to the backup server, and is duplicated and held by the backup server.

  By creating mail data in units of mail, it is possible to include update contents such as adding mail to a mailbox and deleting mail from the mailbox as one unit in the mail data. In addition, for example, by copying the mail data including a UID that is a logical identifier in the protocol as identification information, the mail server and the backup server hold the mail having the same UID, Similarly, the mail client can correctly identify individual mails in the backup server.

  In this way, by updating update information such as addition and deletion of mail and mail identification information as mail data together with the mail body, the correspondence between the mail body and the identification information (UID) is the same between the mail server and the backup server. Even if the operation is switched from the mail server to the backup server, the use can be started without receiving the same mail again on the mail client side.

  In addition, the network bandwidth required between the mail server and the backup server does not require a large bandwidth to guarantee the order as compared with the disk I / O unit duplication by the storage device, and several M to several tens of Mbyte / Since practical mail replication is possible in a bandwidth of about sec, it is advantageous in terms of cost and feasibility.

  By storing a record (log) when copying mail data including the mail body, mail identification information, and mail update information, the copy status can be confirmed in mail units, and in disk I / O units by the storage device. It becomes useful information as a mail server compared with the copy of.

  Furthermore, the above-described duplication processing is realized by software and is performed asynchronously while ensuring that no mail is lost. By performing the processing asynchronously, it is possible to reduce the load on normal mail transmission / reception processing.

  The present invention creates a mailbox that holds a mail received from a mail client or a mail delivery server and updates the created mailbox, and holds the mailbox and information about the mailbox as backup data. A backup system for a mail server comprising a backup server, wherein the mail server is a duplication mailbox data file containing information about the mailbox and the mailbox in a process of creating or updating the mailbox Is created in units of mailboxes, and the copy mailbox data file is transmitted to the backup server, and the backup server transmits the duplicate mailboxes transmitted from the mail server. Reads over datafile may be a mail server backup system, which comprises duplicate information on the mailbox and the mailbox.

  The present invention also provides a mail server that holds mail received from a mail client or a mail delivery server in a mailbox, a backup server that holds mail held in the mailbox and information related to the mail as backup data, A mail server backup method comprising: a mail unit storing a mail data file for duplication including mail held in the mailbox and information related to the mail in a process of holding the mail; And the copy mail data file is transmitted to the backup server, and the backup server reads the copy mail data file transmitted from the mail server, and stores the mail stored in the mailbox and the mail data file. It may be a backup method of the mail server, characterized by duplicating the information about Lumpur.

  The present invention also provides a mail server that creates a mailbox that holds mail received from a mail client or a mail delivery server and updates the created mailbox, and the mailbox and information related to the mailbox as backup data. A backup method for a mail server comprising a backup server to be stored, wherein the mail server includes a mailbox for duplication including information on the mailbox and the mailbox in a process of creating or updating the mailbox A data file is created for each mailbox, and the copy mailbox data file is sent to the backup server. The backup server sends a copy mailbox sent from the mail server. It reads the data file may be a backup method of the mail server, characterized by replicating information on the mailbox and the mailbox.

  Further, the present invention may be a program for causing the mail server and the backup server to execute the mail server backup method described above.

  Further, the present invention may be a recording medium on which the above program is recorded.

  According to the present invention, it is possible to continue service in an equivalent state between the active system and the remote backup environment by performing mail data duplication including mail identification information and mail update information in mail units. A mail server backup system is realized.

  Embodiments of the present invention will be described with reference to the drawings.

<Embodiment 1>
FIG. 1 is a diagram showing a configuration of a mail server backup system according to the present embodiment. The backup system includes an active server 1 and a backup server 2. The servers are connected by an IP (Internet Protocol) network, and mutual data communication by TCP (Transmission Control Protocol) / IP is possible.

  The active server 1 has an SMPT server process 11, a POP server process 12, and a mirror transmission process 13. The active server 1 has mail data (mailbox) 14 and a mirror queue file 15. Yes. The backup server 2 has an SMTP server process 21 and a POP server process 22 operating or waiting, and a mirror reception process 23 is operating. The backup server 2 has mail data (mailbox) 24. Yes.

  FIG. 2 is a diagram showing a flow of a backup operation when adding mail to the mailbox in the active server 1. This is performed by the SMTP server process 11 and the mirror transmission process 13. FIG. 3 is a diagram showing a flow of the backup operation when deleting mail from the mailbox in the active server 1. This is performed by the POP server process 12 and the mirror transmission process 13.

  First, an operation for adding a mail to a mailbox will be described with reference to FIG.

  As a general SMTP server operation, when a mail is received, a queue file including a destination and mail body information is first created. After that, the queue file is read, and if the destination is a mail account owned by itself, additional mail is written to the mailbox, and if the destination is an account of another mail server, transfer processing to another SMTP server is performed. . The queue file that has been processed is deleted.

  In the present embodiment, the operation of the SMTP server process after the queue file reading process is as shown in FIG. First, after reading the queue file (step S211), the SMTP server process 11 writes in the mailbox if the destination is its own account (step S212). Thereafter, a mirror queue file is created (step S213).

  In the mirror queue file, a mail addition instruction, a target (destination) mail address, a mailbox name, a mail UID (for the mail to be added), and information on the mail body are described. After the mirror queue file is created, the queue file is deleted (step S214).

  Next, the mirror transmission process 13 detects that a mirror queue file has been created and reads the file (step S221). Then, the information on the mirror queue file is transmitted to the backup server 2 (step S222). If the transmission process is successful (step S223 / YES), the mirror queue file is deleted (step S224). If the transmission process fails (step S223 / NO), the process proceeds to the next waiting mirror queue file process (step S225), but the mirror queue file that has not been deleted is re-transmitted until it succeeds. The trial continues.

  The mirror reception process 23 of the backup server 2 receives the mirror information transmitted by the mirror transmission process 13 of the active server 1, and is specified in the mailbox (mail data 24) of the mail address specified by the mirror information. Create additional emails with the same UID.

  Next, an operation for deleting a mail from the mailbox will be described with reference to FIG.

  As a general operation of the POP server, after starting a session with a mail client that has been connected, a command from the mail client is first waited. When deleting a mail, when a DELETE command is received, the specified mail is marked for deletion. When a QUIT command is received, the mail marked for deletion is deleted and the session is terminated. To do.

  In the present embodiment, the operation of the POP server process after the start of a session with the mail client is as shown in FIG. First, the POP server process 12 reads a command from the mail client (step S311), performs a command type (step S312), and in the case of a DELETE command, puts a deletion mark on the designated mail (step S313), and next Is awaited (step S314).

  On the other hand, when the QUIT command is received, the mail with the deletion mark is deleted (step S315), and a mirror queue file is created (step S316). In the mirror queue file, information on a mail deletion instruction, a target (destination) mail address, a mailbox name, and a mail UID (for a mail to be deleted) is described. After creating the mirror queue file, the session with the mail client is terminated (step S317).

  Next, the mirror transmission process 13 detects that a mirror queue file has been created, and performs read processing (step S321). Information on the mirror queue file is transmitted to the backup server 2 (step S322). If the transmission process is successful (step S323 / YES), the mirror queue file is deleted (step S324). On the other hand, if the transmission process has failed (step S323 / NO), the process proceeds to the process of the mirror queue file to be standby next (step S325). Mirror queue files that have not been deleted continue to be retried until successful.

  The mirror reception process 23 of the backup server 2 receives the mirror information transmitted by the mirror transmission process 13 of the active server 1, and is designated in the mailbox (mail data 24) of the mail address designated by the mirror information. Delete the UID mail.

  According to the above-described embodiment, the data transmitted from the mirror transmission process to the backup server is the operation instruction (adding or deleting mail), target (destination) mail address, mailbox name, mail UID for one mail. The mail body. This means that the amount of data transferred between the active server and the backup server for replication is significantly smaller than that of the conventional method of synchronizing storage devices, and is almost equivalent to SMTP mail transfer, It shows that practical replication is possible in a band of about several M to several tens of Mbyte / sec. In the method of synchronizing the storage devices, it is necessary to transfer all the disk I / O information. Therefore, it is considered that the required network bandwidth is significantly larger than the method according to the present embodiment. The small required network bandwidth means that it is advantageous in terms of cost and feasibility when constructing a backup environment in a remote place.

  Further, according to the above-described embodiment, the mail update information (addition, deletion) and the mail identification information (UID) are reflected on the backup server, and the number of mails present in the mailboxes between the active server and the backup server and Mail identification information (UID) is held the same. This indicates that the mail client will not receive unnecessary mail (for example, mail that has already been received) when starting to use the backup environment, compared to the conventional SMTP mail transfer method. Therefore, the same operation as the synchronization method of the storage device is realized.

  Further, according to the above-described embodiment, the creation of the mirror queue file when adding mail is performed before the queue file is deleted. This indicates that the creation of the mirror queue file is completed when the mail reception is completed. The mirror queue file is retried without being deleted until it is successfully sent to the backup server. These procedures ensure that no mail is lost.

  In addition, according to the above-described embodiment, the mirror transmission process operates as a separate process from the SMTP server process and the POP server process, thereby performing the replication process asynchronously. This indicates that the replication process is realized without greatly affecting the operations of the SMTP server process and the POP server process.

<Embodiment 2>
In the present embodiment, for creating and deleting a mailbox in the IMAP protocol, it is possible to realize a backup environment in the mailbox by performing duplication while maintaining the identity of UIDVALIDITY.

  UIDVALIDITY is a unique identifier (numerical value) assigned to a mailbox, and is used by the mail client to correctly identify the mailbox in the IMAP protocol. By maintaining the correspondence between the mailbox and UIDVALIDITY in the active server and the backup server, the IMAP client can correctly refer to the same mailbox as that in the active server at the start of using the backup server.

  FIG. 4 is a diagram showing a flow of backup operation when a mailbox is created, deleted, or renamed in the active server 1. This will be specifically described below.

  As a general operation of the IMAP server, a command from the mail client is first waited after starting a session with the mail client that has been connected. As an operation for creating a mailbox, a designated mailbox is added when a CREATE command is received. As an operation for deleting a mailbox, when a DELETE command is received, a deletion mark is added to the designated mailbox for deletion. As an operation for changing the name of the mailbox, when a RENAME command is received, the name is changed by attaching a name change mark to the designated mailbox.

  First, the IMAP server process 42 reads a command from the mail client (step S411) and performs a command type (step S412). If it is a CREATE command, a mailbox is created (step S413), and a mirror queue file for the creation is created (step S414). Then, it waits for the next command (step S415).

  If the command type is a DELETE command, the mailbox is deleted (step S416), a mirror queue file for the deletion is created (step S417), and after the creation, the next command is waited (step S418). . If the command is a RENAME command, the mailbox name is changed (step S419), a mirror queue file for the name change is created (step S420), and the next command is awaited (step S421).

  The contents of the mirror queue file described above include mailbox operation instructions (creation, deletion, name change), target mail address, target mailbox name, new mailbox name (in case of name change), and UIDVALIDITY information. .

  Next, the mirror transmission process 13 detects that a mirror queue file has been created, and performs a read process (step S431). The mirror transmission process 13 transmits the read mirror queue file information to the backup server 2 (step S432).

  If the transmission process is successful (step S433 / YES), the mirror queue file is deleted (step S434). If the transmission process fails (step S433 / NO), the process of the mirror queue file to be waited for next is performed. (Step S435). Mirror queue files that have not been deleted continue to be retried until successful.

  The mirror reception process 23 of the backup server 2 receives the mirror information transmitted by the mirror transmission process 13 of the active server 1, and creates, deletes, or renames the mailbox specified by the mirror information.

  As described above, the mirror reception process of the backup server 2 reflects the received mirror information, so that the active server 1 and the backup server 2 can maintain the same mailbox configuration.

  A computer-readable recording medium that records a program code of software that realizes the functions of the embodiments of the present invention described above, that is, a storage medium, is supplied to an operational server and a backup server, and the operational server and the backup server The object of the present invention is also achieved by reading and executing the program code stored in the storage medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  Examples of the storage medium for supplying the program code include a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a nonvolatile memory card, a ROM, and a magnetic tape. Can be used.

  The above-described embodiment is a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiment alone, and various modifications are made without departing from the gist of the present invention. Implementation is possible.

It is the figure which showed the structure of the backup system of the mail server which concerns on embodiment of this invention. It is the figure which showed the flow of the backup operation | movement in the backup system of the mail server which concerns on embodiment of this invention. It is the figure which showed the flow of the backup operation | movement in the backup system of the mail server which concerns on embodiment of this invention. It is the figure which showed the flow of the backup operation | movement in the backup system of the mail server which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Active server 2 Backup server 11, 21 SMTP server process 12, 22 POP server process 13 Mirror transmission process 14, 24 Mail data (mailbox)
15 Queue file for mirror 23 Mirror reception process 42 IMAP server process

Claims (14)

It consists of an operational mail server that holds mail received from a mail client or mail delivery server in a mailbox, and a backup mail server that holds the mail held in the mailbox and information related to the mail as backup data. A mail server backup system
The operational mail server creates a mail data file for duplication including the mail held in the mailbox and information related to the mail in a unit of mail in the process of holding the mail, and the mail data file for duplication To the backup mail server ,
The mail server backup system , wherein the backup mail server reads the duplication mail data file transmitted from the operational mail server, and duplicates the mail held in the mailbox and information related to the mail. The operational mail server creates a duplication mail data file in the process of holding the mail and transmits the duplication mail data file to the backup mail server in the process of reading the duplication mail data file. 2. The mail server backup system according to claim 1, wherein the mail server is performed as a separate process and in the order in which the mail is updated.   The mail server backup system according to claim 1, wherein the information on the mail includes mail update history information and logical mail identification information on a protocol. An operational mail server that creates a mailbox that holds mail received from a mail client or a mail delivery server and updates the created mailbox, and a backup mail that holds information about the mailbox and the mailbox as backup data A mail server backup system comprising a server,
In the process of creating or updating the mailbox, the operational mail server creates a duplication mailbox data file including the mailbox and information about the mailbox for each mailbox, and creates the duplication mailbox Send the data file to the backup mail server ,
The mail server backup system , wherein the backup mail server reads the duplication mailbox data file transmitted from the operational mail server, and duplicates the mailbox and information related to the mailbox. The operational mail server creates the duplication mailbox data file in the process of creating the mailbox and reads the backup mail of the duplication mailbox data file in the process of reading the duplication mailbox data file. 5. The mail server backup system according to claim 4, wherein the transmission to the server is performed as a separate process and in the order in which the mailboxes are updated.   6. The mail server backup system according to claim 4, wherein the information about the mailbox includes mailbox update history information and logical mailbox identification information on a protocol. It consists of an operational mail server that holds mail received from a mail client or mail delivery server in a mailbox, and a backup mail server that holds the mail held in the mailbox and information related to the mail as backup data. A backup method for a mail server,
The operational mail server creates a mail data file for duplication including the mail held in the mailbox and information related to the mail in a unit of mail in the process of holding the mail, and the mail data file for duplication To the backup mail server ,
The mail server backup method, wherein the backup mail server reads the duplication mail data file transmitted from the operational mail server, and duplicates the mail held in the mailbox and information related to the mail. The operational mail server creates a duplication mail data file in the process of holding the mail and transmits the duplication mail data file to the backup mail server in the process of reading the duplication mail data file. The mail server backup method according to claim 7, wherein the mail server is performed as a separate process and in the order in which the mail is updated.   9. The mail server backup method according to claim 7, wherein the information on the mail includes mail update history information and logical mail identification information on a protocol. An operational mail server that creates a mailbox that holds mail received from a mail client or a mail delivery server and updates the created mailbox, and a backup mail that holds information about the mailbox and the mailbox as backup data A mail server backup method composed of a server,
In the process of creating or updating the mailbox, the operational mail server creates a duplication mailbox data file including the mailbox and information about the mailbox for each mailbox, and creates the duplication mailbox Send the data file to the backup mail server ,
The mail server backup method, wherein the backup mail server reads the duplication mailbox data file transmitted from the active mail server, and duplicates the mailbox and information related to the mailbox. The operational mail server creates the duplication mailbox data file in the process of creating the mailbox and reads the backup mail of the duplication mailbox data file in the process of reading the duplication mailbox data file. The mail server backup method according to claim 10, wherein the transmission to the server is performed as a separate process and in the order in which the mailboxes are updated.   12. The mail server backup method according to claim 10, wherein the information on the mailbox includes mailbox update history information and logical mailbox identification information on a protocol. A program for causing the operational mail server and the backup mail server to execute the mail server backup method according to claim 7.   A recording medium on which the program according to claim 13 is recorded.

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