Power consumption control on an identified unused storage unit

A storage system that functions as one or more logical volumes includes a control unit and a plurality of storage units connected to the control unit, wherein the control unit includes a memory that stores allocation status information that indicates status of allocation of the plurality of storage units to a logical volume; an access request responding unit that controls at least one storage unit among the plurality of storage units in response to a request for access to each logical volume from a host device; and a power saving controller that identifies an unused storage unit not allocated to any logical volume among the plurality of storage units on the basis of the allocation status information and performs power saving control on the identified unused storage unit.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2012-138580, filed on Jun. 20, 2012, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a storage system and a power consumption control method for the storage system.

BACKGROUND

There is a storage apparatus configured as illustrated inFIG. 1. A base device110in this storage apparatus is connected to the host via a fiber channel or the like and functions even alone (i.e., with no add-on devices120connected thereto) as a storage. The add-on devices120have a plurality of disk drives incorporated therein and are daisy-chained to the base device110to implement a large-capacity storage system.

The total storage capacity of this storage apparatus may be increased, therefore, by adding add-on devices120. When installing this storage apparatus in a large-scale data center or the like, the maximum number of add-on devices120are sometimes incorporated in the storage apparatus such that add-on devices120does not have to be installed in the future.

In such a case, the add-on devices120that are incorporated in the storage apparatus for future extension of the storage capacity and are currently not used at all (referred to hereinafter as extra add-on devices120) consume electric power. It is desirable, therefore, to reduce the power consumption by the extra add-on devices120, but, in conventional storage apparatus, there is no way but to manually turn off the power switches of the add-on devices120to reduce the power consumption by the extra add-on devices120.

Japanese Laid-open Patent Publication Nos. 2008-90352 and 2008-276341 discuss the power consumption control for a storage apparatus (system).

Problems to be solved by the disclosed technology are to provide a storage system that automatically controls the power consumption by the extra storage units in the storage system and to provide a power consumption control method for the storage system to automatically control the power consumption by the extra storage units in the storage system.

SUMMARY

According to an aspect of the embodiments, a storage system that functions as one or more logical volumes includes a control unit and a plurality of storage units connected to the control unit, wherein the control unit includes a memory that stores allocation status information that indicates status of allocation of the plurality of storage units to a logical volume; an access request responding unit that controls at least one storage unit among the plurality of storage units in response to a request for access to each logical volume from a host device; and a power saving controller that identifies an unused storage unit not allocated to any logical volume among the plurality of storage units on the basis of the allocation status information and performs power saving control on the identified unused storage unit.

DESCRIPTION OF EMBODIMENTS

Several embodiments are described in detail with reference to the drawings.

First Embodiment

FIG. 2illustrates the structure of a storage system according to a first embodiment. Referring first toFIG. 2, the storage system according to the present embodiment is outlined focusing on the hardware configuration thereof.

As illustrated inFIG. 2, the storage system according to the present embodiment has a controller enclosure (CE)10that includes a power supply unit (PSU)18, controller module (CM)11, and a plurality of disk drives30. The storage system also has N drive enclosures (DE)20that each includes a power supply unit (PSU)28, an expander module (EM)21, and a plurality of disk drives30.

PSU28in DE20is a unit that converts AC power to DC power and supplies the converted DC power to the units in DE20. PSU28has a built-in fan to cool the disk drives30(also referred to hereinafter as disks30) etc. in DE20. PSU28is equipped with a plurality of output terminals that output DC power (such as output terminals that supply electric power to the disks30, an output terminal that supplies electric power to an expander chip (EXP chip)24, and output terminals that supply electric power to the units in EM21other than the EXP chip24). PSU28enables the turning on and off of the fan and the turning on and off of the output from each output terminal to be controlled from outside.

EM21is a module that basically performs control operations on the disks30in the current DE20in response to the commands from CM11addressed to the current DE20and sends the other commands to the subsequent DE20.

As illustrated inFIG. 2, EM21includes a power supply control module23, an expander chip (EXP chip)24, a repeater25, and a signal monitor26.

The power supply control module23is a unit (field-programmable gate array (FPGA) in the present embodiment) that controls PSU28to place DE20in one of the following three modes.—Normal mode in which electric power is supplied to all the units in DE20; —first power saving mode in which electric power is supplied to the units in EM21but not to the disks30, and the fan in PSU28is stopped; and —second power saving mode in which electric power is supplied to the power supply control module23, repeater25, and signal monitor26but not to the EXP chip24and the disks30, and the fan in PSU28is stopped.

More specifically, the power supply control module23operates as follows.

Upon start-up of the storage system, the power supply control module23controls PSU28to place DE20in the second power saving mode. Receiving a request for transition to normal mode with a predetermined content from the signal monitor26, the power supply control module23controls PSU28to place DE20in the normal mode. Receiving a request for transition to first power saving mode with a predetermined content from the EXP chip24, the power supply control module23controls PSU28to place DE20in the first power saving mode. Receiving a request for transition to second power saving mode with a predetermined content from the EXP chip24, the power supply control module23controls PSU28to place DE20in the second power saving mode.

The repeater25is a unit (a chip having an amplification function) that relays the signals to be transmitted between the EXP chip24in the current EM21and the EXP chip14or24in the preceding enclosure (CE10or DE20).

The signal monitor26is a unit (FPGA in the present embodiment) that detects COMINIT and COMWAKE out of the signals received by the repeater25from the preceding enclosure and, when detecting either one of these signals, sends a request for return to normal mode to the power supply control module23. Both COMINIT and COMWAKE are signals used in the out-of-band (OOB) sequence.

The EXP chip24is a SAS expander chip that connects between the EXP chip14or24in the preceding enclosure and the EXP chip24in the subsequent DE20or each drive30in the current DE20.

When activated by the electric power supplied from PSU28, this EXP chip24inquires the signal monitor26which of COMINIT or COMWAKE has been received to cause the signal monitor26to send the request for return to normal mode. If COMINIT has caused the signal monitor26to send the request for return to normal mode, the EXP chip24initiates an OOB sequence to the subsequent DE20(EM21).

Like PSU28, PSU18in CE10is a unit that is equipped with a fan that cools the disk drives30etc. and a plurality of output terminals that output DC power and enables the turning on and off of the fan and the turning on and off of the output from each output terminal to be controlled from outside.

CM11is a module that receives a request for access to each logical volume from the host (not illustrated) and controls operations (read/write access) to each logical volume in accordance with the content of the received access request.

Term “logical volume” refers here to a group of disks30in the storage system that may be handled as a single storage device by the host. The setting (registration or cancellation) of a logical volume in the storage system is usually performed by operating a computer connected to CE10via a local area network (LAN). The present storage system allows the disks30in the system to be managed as several RAID groups and several logical volumes to be set in each RAID group.

As illustrated inFIG. 2, CM11includes a control chip12, a power supply control module13, and an expander chip (EXP chip)14. CM11also has a memory15, which includes a flash read only memory (ROM) having a firmware stored therein and a random access memory (RAM), an interface circuit (not illustrated) that connects to the host via a fiber channel or the like, a LAN port (not illustrated), etc.

The control chip12in CM11is a processor that executes the firmware stored in the memory15and the programs stored in a specific disk30(disk30used as the system disk) in CE10. When activated, the control chip12(a program executed by the control chip12) initiates an OOB sequence to the subsequent DE20(i.e., initiates a process to exchange signals for the OOB sequence using the EXP chip14).

The EXP chip14is a SAS expander chip that connects between the control chip12and the other units (i.e., power supply control module13and each drive30in CM11and the subsequent DE20).

The power supply control module13is a module (FPGA in the present embodiment) that performs control operations on PSU18as instructed by the control chip12(i.e., controls the turning on and off of the fan and the turning on and off of the output from each output terminal). Upon start-up of the storage system, the power supply control module13controls PSU18to place CE10in a mode in which electric power is supplied to the units in CE10.

The operations described above are described more specifically. In the following description, DE #M refers to the DE20connected to CE10via M−1 DEs20.

As is clear from the above description of the function of each unit, upon start-up of the storage system, each unit in the storage system operates as follows.

Upon start-up of the storage system, PSU18in CE10starts supplying electric power to the units in CE10. PSU28in each DE20starts supplying electric power to the power supply control module23, repeater25, and signal monitor26in the DE20and thereby places the DE20in the second power saving mode.

Supplied with electric power, the control chip12in CE10starts operating and initiates an OOB sequence. A COMINIT signal is accordingly input to the repeater25in DE #1. Upon detecting the COMINIT signal, the signal monitor26in DE #1outputs a request for transition to normal mode to the power supply control module23to cause DE #1to transition to the normal mode.

When activated by the electric power supplied by PSU28, the EXP chip24in DE #1inquires the signal monitor26which of COMINIT or COMWAKE has been received to cause the signal monitor26to send the request for return to normal mode. In this case, COMINIT has caused the signal monitor26to send the request for return to normal mode, so the EXP chip24initiates an OOB sequence to the subsequent DE #2.

Since a similar process takes place in DE #3and subsequent DEs20, all the DEs20are placed in the normal mode (referred to hereinafter as an initial state) upon start-up of the storage system.

Next, operations of the storage system after the initial state is established are described.

Once the OOB sequence is completed, CM11(the control chip12in CM11) waits for a prescribed time period (e.g., 30 minutes) to elapse. While waiting for the prescribed time period to elapse, if a logical module and/or hot spare is set, CM11stores in the memory15these settings, such as a logical module setting status in each DE20, as the logical module setting status information arranged in the order of DEs20as illustrated inFIG. 3, for example. Term “hot spare” (“HS” inFIG. 3) refers to a disk being in a hot standby state as a replacement for a failed disk.

Once the prescribed time period elapses, CM11performs a power saving control process following the procedure illustrated inFIG. 4.

More specifically, once the prescribed time period elapses, CM11having initiated this power saving control process sets a variable M to the number of DEs20in the current system (referred to hereinafter as the DE count) (operation S101).

CM11then determines whether DE #M is in use or not on the basis of the logical module setting status information (FIG. 3) (operation S102). More specifically, when no disk30in DE #M is set as an element of the logical volume or hot spare (referred to hereinafter as a logical volume etc.), CM11determines that DE #M is not in use in operation S102. When at least one disk30in DE #M is set as a logical volume etc., CM11determines that DE #M is in use.

When DE #M is not in use (operation S102; NO), CM11determines whether or not one or more in-use DEs (DEs determined to be in use in operation S102) are present among the DEs behind DE #M (referred to hereinafter as subsequent DEs) (operation S103). In other words, CM11determines whether or not one or more in-use DEs are present among the subsequent DEs on which the decision in operation S102has been made.

If no in-use DEs are found among the subsequent DEs (operation S103; NO), CM11places DE #M in the second power saving mode by instructing DE #M to effect a transition to the second power saving mode (operation S105). If one or more in-use DEs are present among the subsequent DEs (operation S103; YES), CM11places DE #M in the first power saving mode by instructing DE #M to effect a transition to the first power saving mode (operation S104). Phrase “instructing DE #M to effect a transition to the I-th (I=1 or 2) power saving mode” means that “a request is sent to DE #M to cause the EXP chip24in DE #M to send a request for transition to the I-th power saving mode to the power supply control module23”.

In the second power saving mode, electric power is less consumed than in the first power saving mode. From the viewpoint of power consumption, it is desirable that the DEs20in which the disks30do not have to be supplied with electric power are placed in the second power saving mode. In the present storage system, however, no communication is established between a DE #X and CE10when the EXP chip24is not operating in any one of the DEs20between DE #X and CE10. For this reason, when at least one in-use DE (DE20with which CE10has to establish communication) is present among the subsequent DEs, DE #M transitions to the first power saving mode, not to the second power saving mode.

After processing in operation S104or S105, CM11decrements the M value by “1” (operation S106). When DE #M is in use (operation S102; YES), CM11decrements the M value by “1” without processing in operations S103etc. (operation S106).

When the decremented M value is not “0” (operation S107; NO), CM11returns to operation S102and repeats processing.

CM11repeats processing in operations S102to S106until the M value reaches “0”. When the M value reaches “0” (operation S107; YES), CM11completes this power saving control process.

After completing the power saving control process, CM11enters a state in which CM11monitors the reception of an access request from the host, addition of a DE20(connection of a new DE20to the trailing-end DE20), change of settings related to the logical volume and/or hot spare, etc.

Receiving an access request from the host, CM11controls several disks30in the system in response to the access request.

When a DE20is added, CM11initiates a power saving control process for the added DE following the procedure illustrated inFIG. 5. More specifically, when a DE20(referred to hereinafter as the additional DE) is added, CM11first sets an energy saving control counter to an initial value (e.g., “1800”) (operation S201). The energy saving control counter is a variable the value of which is stored in the RAM in the memory15.

Then, during the predetermined time period, CM11monitors whether or not one or more disks30in the additional DE are set as elements of the logical volume, etc. (operations S202to S205). More specifically, CM11performs a “process in which CM11determines whether or not one or more disks30in the additional DE are set as elements of the logical volume etc. on the basis of the logical module setting status information and, when no disk30is set as an element of the logical volume etc., decrements the energy saving control counter by “1”, and then CM11determines whether or not the counter value reaches “0”” at intervals of a predetermined number of seconds (e.g., 1 second).

When one or more disks30in the additional DE are set as elements of the logical volume etc. (operation S202; NO/operation S203; YES) before the predetermined time period (e.g., time period depending on the initial value of the energy saving control counter) elapses, CM11terminates the power saving control process for the additional DE without changing the mode of the additional DE. When no disk30in the additional DE is set as an element of the logical volume etc. before the predetermined time period elapses (operation S205; YES), CM11changes the mode of the additional DE to the second power saving mode by instructing the additional DE to effect a transition to the second power saving mode (operation S206). Then, CM11completes the power saving control process for the additional DE.

Operations performed by CM11after the setting for logical module and/or hot spare is changed (registration or cancellation) are described.

When the registration for logical module and/or hot spare is made, CM11performs a first mode control process following the procedure illustrated inFIG. 6.

More specifically, after the registration for logical module etc. is made, CM11first determines whether or not one or more DEs20in the second power saving mode (referred to hereinafter as the second type DE) are present among the DEs preceding the DE20in which the registration for logical module etc. has been made (operation S301).

When one or more second type DEs are present among the preceding DEs (operation S301; YES), CM11changes the mode of each second type DE to the first power saving mode successively starting with the most preceding second type DE (operation S302). The process that CM11actually performs in operation S302is a process in which CM11instructs the DE20preceding each second type DE to send COMWAKE to the next DE20, successively starting with the most preceding second type DE.

After processing in operation S302, CM11changes the mode of the DE20that has become an in-use DE as a result of the registration as an element of the logical module etc. (referred to hereinafter as the target DE) to the normal mode (operation S303). If no second type DE is present among the preceding DEs (operation S301; NO), CM11performs processing in operation S303without processing in operation S302.

In operation S303, CM11performs processing depending on the mode of the target DE. More specifically, if the target DE is in the first power saving mode, CM11performs processing to instruct the target DE to effect a transition to the normal mode. If the target DE is in the second power saving mode, CM11performs processing to instruct the DE20preceding the target DE to send COMWAKE to the next DE20(i.e., target DE).

After processing in operation S303, CM11completes the first mode control process.

When the registration for a logical module or hot spare is cancelled, CM11performs a second mode control process following the procedure illustrated inFIG. 7.

More specifically, upon initiating the second mode control process, CM11first sets a variable M to “1” (operation S401). Then, CM11determines whether DE #M is currently in the normal mode, first power saving mode, or second power saving mode (operation S402).

If DE #M is currently in the second power saving mode (operation S402; second power saving mode), CM11instructs DE #M−1 to send COMWAKE to DE #M (operation S403). When M=1, CM11sends COMWAKE to DE #1in operation S403.

If DE #M is currently in the first power saving mode (operation S402; first power saving mode), CM11instructs DE #M to effect a transition to the normal mode (operation S404).

After processing in operation S403or S404, CM11increments the M value by “1” (operation S405). If DE #M is currently in the normal mode (operation S402; normal mode), CM11increments the M value by “1” (operation S405) without processing in operation S403or S404.

Subsequently, CM11determines whether or not the incremented M value matches the DE count (operation S406). If the M value does not match the DE count (operation S406; NO), CM11returns to operation S402to repeat processing.

If the M value matches the DE count (operation S406; YES), CM11performs the power saving control process described above (FIG. 4) in operation S407and then completes the second mode control process.

As described above, the storage system according to the present embodiment has the function of automatically controlling the transition of the DEs in which no disk30is used as an element of the logical module (or hot spare) to the second power saving mode in which power consumption is very low. For the DEs that are actually used, settings are made to allocate several disks30as the elements of the logical module, while for the extra DEs20, settings for the logical module are not made. Accordingly, it may be said that the storage system according to the present embodiment automatically controls the power consumption of the extra storage units in the system.

Second Embodiment

Referring now toFIG. 8, the configuration and operations of a storage system according to a second embodiment is described, focusing on differences from the storage system according to the first embodiment described above.

As illustrated inFIG. 8, the storage system according to the second embodiment includes a CE10and a plurality of DEs20b.

The CE10in the storage system according to the second embodiment is the same as the CE10provided in the storage system according to the first embodiment. Each DE20bin the storage system according to the second embodiment includes EM21b, instead of the EM21provided in each DE20in the storage system according to the first embodiment.

A power supply control module23bin EM21bis a unit that has basically the same function as the power supply control module23provided in EM21. The power supply control module23b, however, receives a request for return to normal mode from an EXP chip24b.

The EXP chip24bin EM21bis a unit that has functions of the repeater25and signal monitor26in addition to the function of the EXP chip24. The EXP chip24benables electric power to be supplied separately to the portion that functions as the EXP chip24and to the portion that functions as the repeater25and signal monitor26(i.e., the unit is equipped with the so-called power gates).

The storage system according to the present embodiment is different from the storage system according to the first embodiment in that the EXP chip24, repeater25, and signal monitor26are implemented in a single chip. Accordingly, it may be said that the storage system according to the second embodiment automatically controls the power consumption of the extra storage units in the system.

Third Embodiment

Referring now toFIG. 9, the configuration and operations of a storage system according to a third embodiment is described, focusing on differences from the storage system according to the first embodiment described above.

As illustrated inFIG. 9, the storage system according to the third embodiment includes CE10cand a plurality of DEs20c.

DE20cis a device that includes an EM21cinstead of the EM21provided in DE20. The EXP chip24cin EM21cis a SAS expander chip having no function for OOB sequence. The power supply control module23cin EM21ccontrols PSU28in response to instructions from the power supply control module13cin CE10c(instructions given via a dedicated hardware signal line in the present embodiment) to place DE20cin one of the following three modes.—Normal mode in which electric power is supplied to all the units in DE20c; —first power saving mode in which electric power is supplied to the power supply control module23cand EXP chip24cin EM21cbut not to the disks30, and the fan in PSU28is stopped; and —second power saving mode in which electric power is supplied to the power supply control module23cbut not to the EXP chip24cand disks30, and the fan in PSU28is stopped.

The power supply control module23cis a unit that controls PSU28to place DE20cin the second power saving mode upon start-up of the storage system.

CE10cis a device that includes CM11cinstead of CM11provided in CE10. The power supply control module13cin CM11cis a unit that sends the commands given by the control chip12via the EXP chip14to the power supply control module23cin the DE20cdesignated by the control chip12.

The storage system according to the present embodiment is a system that is programmed such that the control chip12performs basically the same mode control operations as the control chip12provided in CM11by issuing commands to the power supply control module23cin each DE20cvia the power supply control module13c, etc.

Fourth Embodiment

The configuration and operations of a storage system according to a fourth embodiment is described, focusing on differences from the storage system according to the first embodiment described above.

FIG. 10schematically illustrates the structure of the storage system according to the fourth embodiment. As illustrated inFIG. 10, the storage system according to the present embodiment has a controller enclosure (CE)10dthat includes two power supply units (PSU)18, two controller modules (CM)11, and a plurality of disk drives30. This storage system also has N drive enclosures (DE)20dthat each includes two PSUs28, two expander modules (EM)21, and a plurality of disk drives30(also referred to hereinafter as disks30).

The units (PSU18, repeater25, etc.) in this storage system are basically the same as the units denoted by the same reference numerals in the storage system according to the first embodiment (FIG. 2). The units in pairs (CM11, PSU28, etc.) in each enclosure are arranged in redundant configuration. If one of the units in pairs (CM11, PSU28, etc.) fails in the storage system, the other unit takes over the processing (power supply to each unit, control of the disks30, etc.) performed by the failed unit. Although not illustrated inFIG. 10, the power supply control module13/23in each CM11/EM21is connected to both PSUs18/28. To enable electric power to be supplied to the unit (CM11/EM21, etc.) to which electric power is not normally supplied, each PSU18/28is connected via a power supply line to the other units.

In the storage system according to the present embodiment, when the units are normally functioning, one control chip12determines the mode of each DE20dand, on the basis of this determination, both control chips12control the power supply mode of the units in the EMs21connected thereto in each DE20d.

As described above, the storage system according to each of the above embodiments has the function of automatically controlling the transition of the DEs in which no disk30is used as an element of the logical module (or hot spare) to the second power saving mode in which power consumption is very low. For the DEs that are actually used, settings are made to allocate several disks30as the elements of the logical module, while for the extra DEs, settings for the logical module are not made. Accordingly, it may be said that the storage system according to each embodiment described above automatically controls the power consumption of the extra storage units in the system.

Variations

Variations may be made to the storage system according to each embodiment described above. For example, the storage system according to each embodiment may be modified such that the power supplying mode is controlled in the units of several drives30in DE, instead of each DE. Furthermore, a storage system in which the enclosures are not differentiated as DE or CE may be implemented on the basis of the technology used in the storage system according to each embodiment.

It will be appreciated that the storage system according to each embodiment may be modified such that, although the same hardware configuration is used, specific processing procedures are different from the above, or the setting as a hot spare is impossible.