JP2010198187A - Method for controlling number of tcp connections of iscsi session, iscsi host device, and configuration program for iscsi initiator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve control of a storage access rate without depending on an application. <P>SOLUTION: In a method for controlling the number of TCP connections, a video server 3 which performs iSCSI session with a plurality of iSCSi targets 2 is configured of reception buffers 4 for storing data to be received in the session, each of which is set with an upper limit threshold and a lower limit threshold, and each of initiators 4 of the video server 3 is integrated with a connection distribution functioning part 5 for distributing iSCSI(Read) commands to TCP connections and a distribution control part 6 for instructing the increase/decrease of the number of TCP connections by using a relation between the upper limit value or lower limit value of the reception buffer 4 and the amounts of the storage data. The distribution control part 6 instructs the decrease of the number of TCP connections when the amounts of the storage data of the reception buffer 4 exceed the upper limit value, and instructs the increase of the number of TCP connections when the amounts of the storage data of the reception buffer 4 become less than the lower limit value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an iSCSI technology for connecting an iSCSI host device and an iSCSI device device using an IP (Internet Protocol) network, and more particularly to a technology for stabilizing a read throughput value.

(1) iSCSI (Internet SCSI, SCSI over TCP)
A storage device composed of a single or a collection of a plurality of hard disk drive devices or a disk array device that controls a plurality of hard disk drive devices with a dedicated control unit has been put into practical use.

  Examples of interface technologies for connecting a storage apparatus (device apparatus) and a host apparatus (server, PC) include Fiber Channel (FC), InfiniBand, and SCSI (Small Computer Systems Interface).

  The SCSI interface is excellent as an application for economically connecting a short distance, and is already widely used. In the interface, a function corresponding to a client is called an initiator, and a function corresponding to a server is called a target, and a SCSI command (CDB: Command Descriptor Block) is exchanged between the initiator and the target.

  As shown in Non-Patent Document 1, iSCSI (Internet SCSI) technology was standardized in 2004 by The Internet Engineering Task Force (RFC3720) as an upper protocol of TCP / IP, which is a network protocol. Unlike other network storage protocols such as Fiber Channel, this iSCSI connection can be used if the computer has an Ethernet (registered trademark) interface.

  Currently, the iSCSI technology is used for a line quality of gigabit or higher, particularly in a backbone line such as in a data center, between data centers, and a large-scale LAN system. The iSCSI technology defines a method of using a plurality of TCP connections in Non-Patent Document 1, but this is not necessarily implemented because of an optional function.

(2) iSCSI speed-up technology On the other hand, the effectiveness of using multiple TCP connections is known as a method for preventing a decrease in iSCSI throughput due to network delay on an IP network having high delay characteristics (Non-Patent Documents). 2.3). In addition, a method using a multilink (see Non-Patent Document 4), a method of changing a transport layer protocol (Non-Patent Document 5), and the like have been proposed as means for realizing multiple use of TCP connections.

  For example, Non-Patent Document 4, which is a technique using a multilink, proposes a technique for establishing a parallel TCP connection through a plurality of routes and using a VPN multihoming function to improve throughput.

  In Non-Patent Document 5, which is a method for changing the protocol of the transport layer, throughput is improved by physically multiplexing links using a plurality of LAN ports and establishing TCP connections through different paths. I am trying.

  However, the technology of Non-Patent Document 4 has a limitation in the environment in which multilink can be used, and the technology of Non-Patent Document 5 still has a problem that it is difficult to connect to a multi-vendor device.

RFC 3720 “Internet Small Computer Systems Interface (iSCSI)”, Apr. 2004. Q. K. Yang “On performance of parallel iSCSI informed storage systems,” In Proceedings of the 20th International Conference on Advanced Information. 1, pp. 629-636, Apr. 2006. G. Motwani and K.M. Gopinath, “Evaluation of advanced TCP stacks in the iSCSI envi- ronment using simulation model,” Proceedings of the 22nd IEEE / 13th NASA Standard. 210-217, 2005. B. K. Kancheria, G .; M.M. Narayan, and K.K. Gopinath, “Performance evaluation of Multiple TCP connection in iSCSI,” in Proceedings of the 24th IEEE Conference on Mass Storage Systems and Tech. 239-244, IEEE Computer Society, Sept. 2007. Nozomi Chishima, Minoru Yamaguchi, Masato Oguchi, “Performance and TCP parameter analysis during VPN multi-path access in iSCSI storage,” IEICE 18th Data Engineering Workshop DEWS 2007), Feb. 2007.

  As described above, in an IP network having high delay characteristics, the problem of a decrease in iSCSI throughput is widely known, and it is also known that a method using TCP multiple connections defined in iSCSI improves the throughput.

  However, there is a server that connects a plurality of iSCSI storages at the same time, and a configuration in which each of a plurality of applications that operate on the server is connected one-to-one with the connected iSCSI storage may cause a problem.

  That is, the fairness of execution of each application is directly linked to the throughput between the storages, and the usage on the server requires that the throughput with the specific storage does not protrude under the usage such as movie playback. Sufficient data access for the input rate must be achieved and the impact on other storage accesses must be kept to a minimum.

  However, conventionally, access control to the IP storage is performed by an application, and it is difficult to achieve fairness unless the access rate is adjusted between applications.

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to realize storage access rate control without depending on an application.

  Although the iSCSI technology defines a function for establishing a plurality of TCP connections in one iSCSI session, issuing a plurality of SCSI commands in parallel, and simultaneously transferring data in each TCP connection, the number of TCP connections is specified. It is not specified how to determine or to which connection a data read / write command from an upper layer is distributed to a plurality of established TCP connections.

  Therefore, in order to solve the above problems, the present invention arranges an algorithm in the initiator for managing which of a plurality of TCP connections the read / write command from the upper layer is distributed to.

  In the case of a read command, the built-in algorithm refers to the receive buffer for each iSCSI session, and distributes the iSCSI (Read / Write) command using the relationship between the upper and lower thresholds set in the receive buffer and the data accumulation amount. Increase or decrease the number of TCP connections. Here, control is performed in advance within the number of connections in which an increase in the number of TCP connections is reflected in an increase in throughput.

  That is, the number of TCP connections that transmit an iSCSI (Read / Write) command when the amount of data received within the iSCSI session reaches an accumulation amount that exceeds the upper limit threshold of the reception buffer is reduced. On the other hand, the number of TCP connections for transmitting an iSCSI (Read / Write) command is increased when the accumulation amount falls below the lower limit threshold of the reception buffer. By performing such control, the amount of data stored in the reception buffer is suppressed to a certain size, and the average throughput is stabilized.

  According to the present invention, the storage access rate is controlled without depending on the application.

Schematic diagram of iSCSI connection using a plurality of TCP connections. The internal block diagram of the video server which concerns on embodiment of this invention. Schematic which shows the example of transmission of the iSCSI command at the time of the TCP multiple connection. Schematic which shows control when the amount of data stored in the reception buffer exceeds an upper threshold. Schematic which shows the control within the range of the upper limit threshold value-the lower limit threshold value in the amount of data stored in the reception buffer. The schematic diagram which shows this control when the accumulation | storage data amount of the same reception buffer is less than a lower limit threshold value.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a basic form in which an iSCSI initiator 1 and an iSCSI target 2 are iSCSI-connected via an IP (Internet Protocol) network.

  Here, in the iSCSI protocol, a plurality of TCP connections are used in one iSCSI connection (iSCSI session). The number of TCP connections is expressed as “N”.

  The iSCSI initiator 1 is mounted on the video server constituting the iSCSI host device, while the iSCSI target 2 is mounted on the disk storage device constituting the iSCSI device device.

  The protocol defined in Non-Patent Document 1 defines a form in which a plurality of TCP connections are used. However, when an iSCSI command from an upper layer is transmitted through a specific TCP connection, the protocol is attributed to the command. It only specifies that "Reception of response from target" and "Response to response" are completed in the same connection.

  In other words, it is not determined whether to change the number N of TCP connections during data transmission / reception in an established iSCSI session, or to which of the established TCP connections an iSCSI (Read / Write) command is transmitted.

  FIG. 2 shows an internal configuration of the video server 3 according to the embodiment of the present invention, and a plurality of iSCSI targets 2 are connected to the video server 3. Each iSCSI target 2 stores data for providing a service.

  The video server 3 includes computer hardware resources (CPU, memory, communication device, etc.). Here, as a result of cooperation between hardware resources and software, the video server 3 receives a group of initiators connected to each iSCSI target 2 on a one-to-one basis and data read from the same iSCSI target 2 through each session. A reception buffer 4 group that is temporarily stored via the initiator 1 is constructed. Each reception buffer 4 is constructed for each iSCSI target 2.

  The function of each iSCSI initiator 1 is realized through a communication device such as an Ethernet interface, and the function of each reception buffer 4 is realized through a storage device such as a memory (RAM). Here, it is assumed that an upper limit threshold and a lower limit threshold for the amount of stored data are set in each reception buffer 4. Each threshold value is defined in a program or the like, and can be changed as appropriate according to the usage situation.

  The video server 3 accesses the data for a specific service operating on the video server 3 stored in each iSCSI target 2 and passes through the reception buffer 4 for the iSCSI target 2 at a predetermined output rate. Send data.

  FIG. 3 shows an example of an iSCSI (Read) command transmission process when the video server 3 is TCP multiple-connected.

  Here, in the iSCSI initiator 1, the connection distribution function unit 5 that distributes iSCSI (Read command) to TCP connections and the increase / decrease in the number of TCP connections that are distributed according to the amount of data stored in the reception buffer 4 are sent to the connection distribution function unit 5. A distribution control unit 6 for instructing is incorporated. Hereinafter, an operation example of the iSCSI initiator 1 will be described.

  First, when an iSCSI (Read) command is issued from an upper layer (read request queue) in the video server 3 as shown by an arrow A in FIG. 3, the command is sent to the iSCSI initiator 1 as shown by an arrow B. Is delivered to the connection distribution functioning unit 5 incorporated in.

  The connection distribution function unit 5 distributes the iSCSI (Read) command received from the upper layer to the TCP connection. Normally, the N TCP connections established (assumed to be No. 1 to N) are assigned in a round-robin manner from No. 1 to No. N. Thus, according to the processing of the connection distribution function unit 5, the arrow C.I. As shown in D, an iSCSI (Read) command is transmitted to the designated TCP connection.

  Next, the data read from the same iSCSI target 2 as described above is temporarily stored in the reception buffer 4. The iSCSI initiator 1 monitors the amount of data stored in the reception buffer 4, and if the upper limit threshold is exceeded or falls below the lower limit threshold, the distribution controller 6 controls the TCP multiplicity as indicated by the arrow E. A signal is sent out.

  When the distribution control unit 6 receives the TCP multiplicity control signal, as shown by an arrow F, the distribution control unit 6 instructs the deletion of the TCP connection to be distributed to the upper threshold or the addition of the TCP connection to be distributed to the lower threshold. An instruction is sent to the connection distribution function unit 5. The connection distribution function unit 5 receives an instruction from the distribution control unit 6 and performs a process of distributing Nos. 1 to n (n is an integer greater than 1 and an integer equal to or less than N) based on a rule such as round robin. An example of the above processing will be described with reference to FIGS.

  FIG. 4 shows a state in which the amount of accumulated data in the reception buffer 4 increases as indicated by the arrow S and exceeds the upper limit threshold P. Here, the TCP multiplicity control signal is sent to the distribution control unit 6, and the distribution control unit 6 sends to the connection distribution function unit 5 an instruction to delete the TCP connection No. 3 from the distribution target. Upon receiving this deletion instruction, the connection distribution function unit 5 performs distribution processing to newly exclude the TCP connection number 3.

  FIG. 5 shows a state in which the amount of data stored in the reception buffer 4 is between the upper limit threshold P and the lower limit threshold Q. Here, the TCP multiplicity control signal is not sent to the distribution control unit 6, and no change occurs in the distribution target (the distribution target remains the TCP connection Nos. 1 to 3).

  FIG. 6 shows a state in which the amount of data stored in the reception buffer 4 decreases as indicated by the arrow R and falls below the lower limit threshold Q. Here, a TCP multiplicity control signal is sent to the distribution control unit 6, and the distribution control unit 6 sends an addition instruction for adding the TCP connection No. 4 to the distribution target to the connection distribution function unit 5. Upon receiving this addition instruction, the connection distribution function unit 5 performs distribution processing for newly adding a TCP connection No. 4. The addition of the number of TCP connections is controlled within the range of the number of connections reflected in the increase in throughput (in FIG. 6, for convenience of explanation, the number is four).

  As described above, the function of distributing the iSCSI (Read) command incorporated in the iSCSI initiator to the TCP connection adjusts the iSCSI reading speed in accordance with the output rate from the video server of the data stored in the iSCSI target without depending on the application. Is possible.

  As a result, the read throughput is stabilized, and the data access sufficient for the input rate required by the application on the video server is realized, while the influence on the access to other iSCSI targets can be minimized.

  The present invention is not limited to the above-described embodiment. For example, the same effect can be expected not only for an iSCSI (Read) command but also for an iSCSI (Write) command.

  The present invention can also be configured as a program for causing a computer to function as the iSCSI initiator 1 incorporating the connection distribution function unit 5 and the distribution control unit 6. In this case, the program is read by a processing unit (for example, CPU) of the computer, and each operation process in FIG. 3 is executed.

  This program can be provided through a network such as a website or e-mail. The program is recorded on a recording medium such as a CD-ROM, DVD-ROM, CD-R, CD-RW, DVD-R, DVD-RW, MO, HDD, Blu-ray Disk (registered trademark). It is also possible to save and distribute. This recording medium is read using a recording medium driving device, and the program code itself realizes the processing of the above embodiment, so that the recording medium also constitutes the present invention.

  Currently, there is a shared server for moving images and the like on the Internet, forming one service area. Here, the storage capacity that can be centrally managed by the server is limited, and the posted videos include those that have almost no access.

  In view of this, it is conceivable to connect the storage on the network through the network on demand so as to mount the DVD medium on the DVD player as necessary, and reproduce the moving image.

  If the iSCSI storage device is used as an on-demand medium corresponding to a DVD medium in such a form, the server is stable and consistent with the playback rate of moving images stored in each iSCSI storage device connected simultaneously. It is desirable to provide a reasonable throughput.

  Conventionally, the application is responsible for reading from the storage device, and only the high speed of the control method is an evaluation criterion. Therefore, the throughput with a specific storage is prominent, and the fairness of service provision may not be achieved. The present invention is particularly effective for fairness of service provision in a video server such as a jukebox via a network.

1 ... iSCSI initiator 2 ... iSCSI target (iSCSI device)
3 ... Video server (iSCSI host device)
4 ... Reception buffer 5 ... Connection distribution function unit 6 ... Distribution control unit P ... Upper threshold Q: Lower threshold

Claims (7)

A method of controlling the number of TCP connections between an iSCSI host device and an iSCSI device device having an iSCSI session with an initiator built in the host device,
A method for controlling the number of TCP connections in an iSCSI session, wherein the number of TCP connections in the session is increased or decreased according to the amount of data stored in the reception buffer of the host device that temporarily stores data received through the iSCSI session. A first step of instructing an increase / decrease in the number of TCP connections using a relationship between a threshold set in the reception buffer and the amount of stored data;
A second step of distributing iSCSI commands to TCP connections according to the instructions of the first step;
The method of controlling the number of TCP connections for an iSCSI session according to claim 1, wherein: The first step instructs to reduce the number of TCP connections when the accumulated data amount exceeds the upper threshold of the reception buffer,
3. The method for controlling the number of TCP connections in an iSCSI session according to claim 2, wherein an increase in the number of TCP connections is instructed when a value falls below a lower threshold of the reception buffer. In the iSCSI host device in which an initiator that performs an iSCSI session with the iSCSI device is constructed,
An iSCSI host device comprising means for increasing / decreasing the number of TCP connections in a session according to the amount of data stored in a reception buffer for temporarily storing data received through an iSCSI session in the initiator. The initiator uses a relationship between a threshold value set in the reception buffer and the amount of stored data, and instructs a distribution control unit to increase or decrease the number of TCP connections;
A distribution function unit that distributes iSCSI commands to TCP connections in accordance with instructions from the distribution control unit;
5. The iSCSI host device according to claim 4, further comprising: The distribution control unit instructs to reduce the number of TCP connections when the accumulated data amount exceeds the upper limit threshold of the reception buffer,
The iSCSI host device according to claim 5, wherein an increase in the number of TCP connections is instructed when a value falls below a lower limit threshold of the reception buffer.   An initiator configuration program for causing a computer to function as the iSCSI host device according to any one of claims 4 to 6.

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