Using locks of different scopes in a data storage system to optimize performance and complexity

Patent metadata

Field	Value
Publication number	US-9864643-B1
Application number	US-201514788732-A
Country	US
Kind code	B1
Filing date	Jun 30, 2015
Priority date	May 5, 2015
Publication date	Jan 9, 2018
Grant date	Jan 9, 2018

Abstract

Embodiments are directed to methods for allowing an I/O path of a data storage system to directly modify an object model while bypassing the highly-contested transaction lock used by a control path. This may be done by introducing a local lock to be used for individual resources within the object model. The control path also uses this local lock mechanism (in the context of a transaction lock) for essential resources that might be accessed by the I/O path in order to avoid accessing a given essential resource at the same time as the I/O path. A data storage system, apparatus, and computer program product for performing similar methods are also provided.

First claim

What is claimed is:

1. A method performed by a data storage system (DSS), the method comprising:
receiving, by an I/O path instance operating on a storage processor of the DSS, a plurality of storage write commands directed at data storage of the DSS;
determining that fulfillment of a first storage write command of the plurality of storage write commands necessitates a change to a particular essential resource of an object model of the DSS, the object model defining settings for resources of objects that describe elements of the DSS;
determining that fulfillment of a second storage write command of the plurality of storage write commands does not necessitate any change to any essential resource within the object model of the DSS;
fulfilling the first storage write command by the I/O path instance:
obtaining a lock on the particular essential resource of the object model, the lock on the particular essential resource preventing any entity other than the I/O path instance operating on the storage processor of the DSS from changing the particular essential resource;
making the change to the particular essential resource within memory of the storage processor while the particular essential resource is locked by the I/O path instance;
subsequent to making the change, releasing the lock on the particular essential resource; and
performing a remainder of the first storage write command with respect to the data storage of the DSS; and

fulfilling the second storage write command by the I/O path instance performing the second storage write command with respect to the data storage of the DSS without obtaining a lock on any essential resource of the object model.

2. The method of claim 1 , wherein the storage processor is a first storage processor and fulfilling the first storage command by the I/O path instance further includes, subsequent to making the change and prior to releasing the lock on the particular essential resource:
writing the change to an object model portion of persistent storage of the DSS; and
synchronizing with a second storage processor of the DSS to ensure that the second storage processor maintains a consistent copy of the object model within memory of the second storage processor.

3. The method of claim 2 , wherein the method further comprises:
subsequent to receiving the first storage write command by the I/O path instance, receiving, by a control path instance operating on one of the first storage processor and the second storage processor of the DSS, a control command directing the control path instance to make another change to the particular essential resource of the object model of the DSS;
obtaining a transaction lock by the control path instance, the transaction lock preventing any other control path instance from changing any essential resource of the object model of the DSS;
subsequent to obtaining the transaction lock, waiting for the lock on the particular essential resource to be released and subsequently obtaining another lock on the particular essential resource by the control path instance, the other lock preventing any entity other than the control path instance from changing the particular essential resource;
making the other change to the particular essential resource within memory of the one of the first storage processor and the second storage processor by the control path instance while the particular essential resource is locked by the control path instance; and
subsequent to making the other change, by the control path instance:
(1) writing the other change to the object model portion of persistent storage of the DSS;
(2) synchronizing with the other of the first storage processor and the second storage processor of the DSS to ensure that both the first storage processor and the second storage processor maintain consistent copies of the object model within memory;
(3) releasing the other lock on the particular essential resource; and
(4) releasing the transaction lock.

4. The method of claim 2 , wherein the method further comprises:
subsequent to receiving the first storage write command by the I/O path instance, receiving, by a control path instance operating on one of the first storage processor and the second storage processor of the DSS, a control command directing the control path instance to make another change to another particular essential resource of the object model of the DSS;
obtaining a transaction lock by the control path instance, the transaction lock preventing any other control path instance from changing any essential resource of the object model of the DSS;
subsequent to obtaining the transaction lock, obtaining another lock on the other particular essential resource by the control path instance, the other lock preventing any entity other than the control path instance from changing the other particular essential resource;
making the other change to the particular essential resource within memory of the one of the first storage processor and the second storage processor by the control path instance while the other particular essential resource is locked by the control path instance; and
subsequent to making the other change, by the control path instance:
(1) writing the other change to the object model portion of persistent storage of the DSS;
(2) synchronizing with the other of the first storage processor and the second storage processor of the DSS to ensure that both the first storage processor and the second storage processor maintain consistent copies of the object model within memory;
(3) releasing the other lock on the other particular essential resource; and
(4) releasing the transaction lock.

5. The method of claim 4 , wherein the method further comprises:
receiving, by another I/O path instance operating on one of the first storage processor and the second storage processor of the DSS, a third storage write command directed at data storage of the DSS;
determining that fulfillment of the third storage write command of the plurality of storage write commands necessitates yet another change to the other particular essential resource;
waiting for the other lock on the other particular essential resource to be released and subsequently obtaining yet another lock on the other particular essential resource by the other I/O path instance, the yet other lock preventing any entity other than the other I/O path instance from changing the other particular essential resource;
making the yet other change to the other particular essential resource within memory of the one of the first storage processor and the second storage processor by the other I/O path instance while the other particular essential resource is locked by the other I/O path instance; and
subsequent to making the yet other change, by the other I/O path instance:
(1) writing the yet other change to the object model portion of persistent storage of the DSS;
(2) synchronizing with the other of the first storage processor and the second storage processor of the DSS to ensure that both the first storage processor and the second storage processor maintain consistent copies of the object model within memory; and
(3) releasing the yet other lock on the other particular essential resource; and
(4) performing a remainder of the third storage write command with respect to the data storage of the DSS.

6. The method of claim 4 , wherein the method further comprises:
receiving, by another I/O path instance operating on one of the first storage processor and the second storage processor of the DSS, a third storage write command directed at data storage of the DSS;
determining that fulfillment of the third storage write command of the plurality of storage write commands necessitates yet another change to yet another particular essential resource

Assignees

• Emc Corp
• Emc Ip Holding Co Llc

Inventors

• Mullis Ii Samuel L
• De Forest Miles A

Classifications

• G06F13/4221 Primary

  being an input/output bus, e.g. ISA bus, EISA bus, PCI bus, SCSI bus · CPC title

• G06F9/526 Primary

  Mutual exclusion algorithms · CPC title