METHOD, DEVICE, AND PROGRAM PRODUCT FOR REDUCING DELAY IN I/O PROCESSING DUE TO MIRRORING OF CACHE DATA

• US 20200133507A1
• Filed: 09/19/2019
• Published: 04/30/2020
• Est. Priority Date: 10/31/2018
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Inventors: Liu, Yousheng, Jia, Ruiyong, Xu, Xinlei
• Granted Patent: US 11,385,796 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/2066 Optimisation of the communication load
• CPC Class Codes: G06F 11/2082 Data synchronisation
• CPC Class Codes: G06F 11/2084 on the same storage unit
• CPC Class Codes: G06F 12/0868 Data transfer between cache memory and other subsystems, e.g. storage devices or host systems
• CPC Class Codes: G06F 12/0882 Page mode
• CPC Class Codes: G06F 2212/1024 Latency reduction
• CPC Class Codes: G06F 2212/262 configured as RAID
• CPC Class Codes: G06F 2212/286 Mirrored cache memory
• CPC Class Codes: G06F 2212/312 In storage controller
• CPC Class Codes: G06F 2212/461 Sector or disk block
• CPC Class Codes: G06F 2212/466 Metadata, control data
• CPC Class Codes: G06F 3/0607 by facilitating the process of upgrading existing storage systems, e.g. for improving compatibility between host and storage device
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0611 in relation to response time
• CPC Class Codes: G06F 3/0635 by changing the path, e.g. traffic rerouting, path reconfiguration
• CPC Class Codes: G06F 3/0656 Data buffering arrangements
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: G06F 9/30123 according to context, e.g. thread buffers

Abstract

Techniques perform storage management. Such techniques involve: in response to receiving, at a first processor of a storage system, a write request from a host for writing user data, caching the user data in a first cache of the first processor, and generating cache metadata in the first cache, the cache metadata including information associated with writing the user data; sending the user data and the cache metadata to a second cache of a second processor, for the second processor to perform, in the second cache, data processing related to cache mirroring by the second processor; and sending, to the host, an indication of completion of the write request, without waiting for the second processor to complete the data processing. Such techniques can improve system performance such as reducing latency, and shortening length of the I/O handling path of write request.

Claims

1. A method of storage management, comprising:

in response to receiving, at a first processor of a storage system, a write request from a host for writing user data to the storage system,

caching the user data in a first cache of the first processor,

generating cache metadata in the first cache, the cache metadata comprising information associated with writing the user data to the storage system;

sending the user data and the cache metadata to a second cache of a second processor of the storage system, for the second processor to perform, in the second cache, data processing related to cache mirroring; and

sending, to the host, an indication of completion of the write request without waiting for the second processor to complete the data processing.

2. The method of claim 1, wherein sending the user data and the cache metadata to the second cache comprises:

transferring the user data from a first physical page of the first cache to a second physical page of the second cache; and

transferring the cache metadata to a receiving buffer of the second cache.

3. The method of claim 2, wherein transferring the cache metadata to the receiving buffer comprises:

encapsulating the cache metadata and recovery information into a cache metadata message, the recovery information being used for recovering the cache metadata message during a failure recovery; and

sending the cache metadata message to the receiving buffer.

4. The method of claim 3, wherein the recovery information comprises at least one of the following:

a processing state, a sending serial number and a checksum of the cache metadata message.

5. The method of claim 4, further comprising:

setting the processing state to “

valid”

to indicate that the cache metadata message has not been processed by the second processor.

6. A method of storage management, comprising:

receiving, at a second processor of a storage system, user data and cache metadata from a first cache of a first processor of the storage system, the cache metadata comprising information associated with writing the user data to the storage system;

preprocessing the cache metadata, such that the user data is accessible to a host via the second processor; and

performing, in a second cache of the second processor, data processing related to cache mirroring based on the user data and the cache metadata.

7. The method of claim 6, wherein receiving the user data and the cache metadata comprises:

transferring the user data from a first physical page of the first cache to a second physical page of the second cache; and

buffering the cache metadata to a receiving buffer of the second cache.

8. The method of claim 7, wherein preprocessing the cache metadata comprises:

moving the cache metadata from the receiving buffer to a queue of cache metadata accessible to the host.

9. The method of claim 8, wherein moving the cache metadata to the queue of cache metadata comprises:

in response to locking successfully a cache page indicated by the cache metadata, moving the cache metadata to a queue of cache metadata to be processed, to wait for processing by the second processor; and

in response to failing to lock the cache page, moving the cache metadata to a waiting queue of cache metadata, to wait for locking the cache page by the second processor for the cache metadata.

10. The method of claim 6, wherein performing the data processing comprises:

adding a physical page storing the user data to a cache page indicated by the cache metadata.

11. The method of claim 6, wherein performing the data processing comprises:

waking up a background thread to perform the data processing.

12. The method of claim 6, further comprising:

in response to receiving an I/O request from the host, preprocessing all cache metadata in the second cache that has not been preprocessed; and

handling the I/O request.

13. The method of claim 6, wherein receiving the cache metadata comprises:

receiving a cache metadata message comprising the cache metadata and recovery information for recovering the cache metadata message during a failure recovery.

14. The method of claim 13, wherein the recovery information comprises at least one of the following:

a processing state, a sending serial number, and a checksum of the cache metadata message.

15. The method of claim 14, further comprising at least one of the follows:

in response to completion of the preprocessing, changing the processing state from an initial value of “

valid”

to “

preprocessed;

”

in response to the data processing being in progress, setting the processing state to “

processing;

” and

in response to the completion of the data processing, setting the processing state to “

invalid.”

16. The method of claim 13, further comprising:

in response to the storage system recovering from a failure, recovering the cache metadata message based on the recovery information.

17. The method of claim 16, wherein recovering the cache metadata message comprises at least one of the following:

determining, based on the processing state, that the cache metadata message is required to be recovered;

determining, based on the sending serial number, a sequence of the cache metadata message and a further recovered cache metadata message; and

checking integrity of the cache metadata message based on the checksum.

18. An electronic device, comprising:

at least two processors; and

at least one memory storing computer program instructions, the at least one memory and the computer program instructions being configured, together with the at least two processors, to cause the electronic device to;

in response to receiving, at a first processor, a write request from a host for writing user data to the storage system,

cache the user data in a first cache of the first processor,

generate cache metadata in the first cache, the cache metadata comprising information associated with writing the user data to the storage system;

send the user data and the cache metadata to a second cache of a second processor, for the second processor to perform, in the second cache, data processing related to cache mirroring; and

send, to the host, an indication of completion of the write request without waiting for the second processor to complete the data processing.

19. An electronic device, comprising:

at least two processors; and

at least one memory storing computer program instructions, the at least one memory and the computer program instructions being configured, together with the at least two processors, to cause the electronic device to;

receive, at a second processor, user data and cache metadata from a first cache of a first processor, the cache metadata comprising information associated with writing the user data to the storage system;

preprocess the cache metadata, such that the user data is accessible to a host via the second processor; and

performing, in a second cache of the second processor, data processing related to cache mirroring based on the user data and the cache metadata.

20. A computer program product having a non-transitory computer readable medium which stores a set of instructions to perform storage management;

the set of instructions, when carried out by computerized circuitry, causing the computerized circuitry to perform a method of;

in response to receiving, at a first processor of a storage system, a write request from a host for writing user data to the storage system,

caching the user data in a first cache of the first processor,

generating cache metadata in the first cache, the cache metadata comprising information associated with writing the user data to the storage system;

sending the user data and the cache metadata to a second cache of a second processor of the storage system, for the second processor to perform, in the second cache, data processing related to cache mirroring; and

sending, to the host, an indication of completion of the write request without waiting for the second processor to complete the data processing.

21. A computer program product having a non-transitory computer readable medium which stores a set of instructions to perform storage management;

the set of instructions, when carried out by computerized circuitry, causing the computerized circuitry to perform a method of;

receiving, at a second processor of a storage system, user data and cache metadata from a first cache of a first processor of the storage system, the cache metadata comprising information associated with writing the user data to the storage system;

preprocessing the cache metadata, such that the user data is accessible to a host via the second processor; and

performing, in a second cache of the second processor, data processing related to cache mirroring based on the user data and the cache metadata.