STORAGE SYSTEM AND I/O REQUEST PROCESSING METHOD FOR STORAGE SYSTEM

1 . A storage system comprising cloud storage which is cloud-based storage, and a storage node for processing an I/O request to the cloud storage,

wherein a processor for the storage node executes an I/O processing thread for retaining an I/O resource including information and a buffer to be used for processing relating to the I/O request and an I/O response transmitted from the cloud storage in response to the I/O request, and a response standby processing thread;

wherein the processor causes the I/O processing thread to:

transmit the I/O request to the cloud storage in response to a request from a host;

perform standby processing for waiting to receive the I/O response to the I/O request after transmitting the I/O request to the cloud storage until an elapse of first time-out time;

transfer the I/O response to the host if having received the I/O response from the cloud storage before the elapse of the first time-out time; and

move the I/O resource to the response standby processing thread and cause the response standby processing thread to retain the I/O resource if not having received the I/O response from the cloud storage before the elapse of the first time-out; and

wherein the processor causes the response standby processing thread to transmit a response confirmation for demanding the I/O response from the cloud storage by using the I/O resource moved from the I/O processing thread and retained by the response standby processing thread and perform the standby processing in place of the I/O processing thread.

2 . The storage system according to claim 1 ,

wherein if the I/O response from the cloud storage is not received by the I/O processing thread before the elapse of the first time-out time,

the processor causes a status transition of the cloud storage from a normal state capable of accepting the I/O request which is new, to a temporary blockade state incapable of accepting the new I/O request and capable of accepting only the response confirmation.

3 . The storage system according to claim 2 ,

wherein the processor measures the number of times when the status of the cloud storage is changed to the temporary blockade state; and

when the number of times reaches an upper limit count, the processor detaches the cloud storage from the storage system.

4 . The storage system according to claim 2 ,

wherein the processor causes the response standby processing thread to:

perform the standby processing after transmitting the response confirmation to the cloud storage until an elapse of second time-out time; and

if having received the I/O response from the cloud storage before the elapse of the second time-out time,

transfer the received I/O response to the host and

release the I/O resource relating to the I/O response retained by the response standby processing thread.

5 . The storage system according to claim 4 ,

wherein if the I/O response from the cloud storage is received by the response standby processing thread before the elapse of the second time-out time,

the processor causes the status transition of the cloud storage from the temporary blockade state to the normal state and

executes difference rebuilding processing for recovering data of the cloud storage.

6 . The storage system according to claim 4 ,

wherein if the I/O response from the cloud storage is not received by the response standby processing thread before the elapse of the second time-out time,

the processor causes the status transition of the cloud storage from the temporary blockade state to a blockade state incapable of accepting the I/O request and the response confirmation and

releases the I/O resource relating to the I/O response retained by the response standby processing thread.

7 . The storage system according to claim 1 ,

wherein the response standby processing thread has a standby request queue and a standby resource queue; and

wherein the processor causes the response standby processing thread to:

retain the I/O resource, which has been moved from the I/O processing thread, in the standby request queue; and

move the I/O resource from the standby request queue to the standby resource queue and execute the standby processing relating to the I/O response which uses the I/O resource.

8 . An I/O request processing method for a storage system and to be executed by the storage system including cloud storage which is cloud-based storage, and a storage node for processing an I/O request to the cloud storage,

wherein a processor for the storage node executes an I/O processing thread for retaining an I/O resource including information and a buffer to be used for processing relating to the I/O request and an I/O response transmitted from the cloud storage in response to the I/O request, and a response standby processing thread;

wherein the processor causes the I/O processing thread to:

transmit the I/O request to the cloud storage in response to a request from a host;

perform standby processing for waiting to receive the I/O response to the I/O request after transmitting the I/O request to the cloud storage until an elapse of first time-out time;

transfer the I/O response to the host if having received the I/O response from the cloud storage before the elapse of the first time-out time; and

move the I/O resource to the response standby processing thread and cause the response standby processing thread to retain the I/O resource if not having received the I/O response from the cloud storage before the elapse of the first time-out; and

wherein the processor causes the response standby processing thread to transmit a response confirmation for demanding the I/O response from the cloud storage by using the I/O resource moved from the I/O processing thread and retained by the response standby processing thread and perform the standby processing in place of the I/O processing thread.