INTELLIGENCE FOR CONTROLLING VIRTUAL STORAGE APPLIANCE STORAGE ALLOCATION

• US 20130086324A1
• Filed: 09/30/2011
• Published: 04/04/2013
• Est. Priority Date: 09/30/2011
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: Gokul Soundararajan
• Inventors: Voruganti, Kaladhar, Bairavasundaram, Lakshmi Narayanan, Mathur, Vipul, Sehgal, Priya, SOUNDARARAJAN, GOKUL
• Granted Patent: US 8,874,848 B2
• Time in Patent Office: Days
• US Class Current: 711/122
• CPC Class Codes: G06F 12/0811 with multilevel cache hierarchies
• CPC Class Codes: G06F 12/0813 with a network or matrix configuration
• CPC Class Codes: G06F 12/0888 using selective caching, e.g. bypass
• CPC Class Codes: G06F 2212/2515 being configurable for different purposes, e.g. as cache or non-cache memory
• CPC Class Codes: G06F 2212/284 being distributed
• CPC Class Codes: G06F 2212/301 In special purpose processing node, e.g. vector processor
• CPC Class Codes: G06F 2212/601 Reconfiguration of cache memory

Abstract

A change in workload characteristics detected at one tier of a multi-tiered cache is communicated to another tier of the multi-tiered cache. Multiple caching elements exist at different tiers, and at least one tier includes a cache element that is dynamically resizable. The communicated change in workload characteristics causes the receiving tier to adjust at least one aspect of cache performance in the multi-tiered cache. In one aspect, at least one dynamically resizable element in the multi-tiered cache is resized responsive to the change in workload characteristics.

Claims

1. A method in a multi-tiered cache comprising:

detecting, by a cache device controller for a tier of the multi-tiered cache, a change of workload characteristics at the tier of the multi-tiered cache, where at least one of the tiers of the multi-tiered cache includes a dynamically resizable cache element, and wherein each tier is managed by a cache device controller; and

communicating the detected change of workload characteristics from the controller to a different controller of a different tier of the multi-tiered cache to cause the different controller to adjust its caching size and policy in response to the detected changes.

2. The method of claim 1, wherein detecting the change of workload characteristics comprises detecting one or more of a change in rate of cache miss, ratio of read versus write input/output (I/O) requests, I/O size, or ratio of random to sequential accesses.

3. The method of claim 1, wherein detecting the change of workload characteristics comprises detecting a change in working set by detecting access to a set of data not already cached.

4. The method of claim 1, wherein detecting the change of workload characteristics comprises detecting a change in a hierarchically highest tier of cache nearest a client, and further comprising communicating the detected change to a controller of a cache tier of a backend storage server.

5. The method of claim 1, wherein to adjust the caching size and policy comprises dynamically de-provisioning a virtual storage appliance (VSA) acting as a cache tier to remove at least a portion of a tier of the multi-tiered cache.

6. The method of claim 1, wherein to adjust the caching size and policy comprises dynamically instantiating a virtual storage appliance (VSA) as a cache tier to increase at least a portion of a tier of the multi-tiered cache.

7. The method of claim 1, wherein to adjust the caching size and policy comprises changing a pre-fetch policy indicating an amount of read-ahead to perform, or changing a caching policy indicating how long to keep data.

8. The method of claim 1, wherein to cause the different tier to adjust caching size and policy comprises to adjust caching size and policy in response to the detected changes only if the detected changes are changed by more than a preconfigured threshold.

9. The method of claim 1, wherein two distinct workloads overlap access to at least a portion of cached data, wherein one of the workloads accesses data through a dynamic cache virtual storage appliance (VSA), and the other workload does not access data through the dynamic cache VSA, and wherein a change in behavior of the workload that does not access data through the dynamic cache VSA causes the dynamic cache VSA to adjust caching size and policy for the other workload.

10. The method of claim 1, wherein to adjust the caching size and policy comprises adjusting a memory allocation size of the dynamically resizable cache element.

11. A storage subsystem comprising:

a storage server having at least one tier of cache;

a dynamic cache virtual storage appliance (VSA) executing in a virtual machine hosted on hardware resources separate from the storage server, the dynamic cache VSA providing a second tier of the cache, the cache being multi-tiered and hierarchical, each tier including a controller to manage the cache tier; and

a communication protocol for cache communication between a controller the first tier of cache at the storage server and a controller of the second tier of cache at the dynamic cache VSA,

wherein at least the first tier of cache at the storage server, or the dynamic cache VSA, or both are dynamically resizable, and

wherein the controllers of the first and second tiers of cache are configured to detect a change of workload characteristics, and to communicate the detected change of workload characteristics to the other controller to cause the other controller to adjust cache size and policy for its cache tier in response to the detected changes.

12. The storage subsystem of claim 11, wherein at least the controller of the second tier of cache is configured to detect one or more of a change in rate of cache miss, ratio of read versus write input/output (I/O) requests, I/O size, or ratio of random to sequential accesses.

13. The storage subsystem of claim 11, wherein to adjust the caching size and policy comprises changing a pre-fetch policy indicating an amount of read-ahead to perform, or changing a caching policy indicating how long to keep data.

14. The storage subsystem of claim 11, wherein the controllers of the first and second tiers of cache are configured to detect a change in workload characteristics only if the detected changes are greater than a threshold.

15. The storage subsystem of claim 11, wherein the storage server is configured to adjust caching size and policy by de-provisioning a virtual storage appliance acting as a tier of dynamic cache to remove at least a portion of a tier of the multi-tiered cache, or by dynamically instantiating a virtual storage appliance as a tier of dynamic cache to increase at least a portion of a tier of the multi-tiered cache.

16. The storage subsystem of claim 11, wherein the controllers of the first and second tiers of cache are further configured to receive a communication from a controller of a different tier of the multi-tiered cache indicating detection by the controller of the different tier of a change of workload characteristics at the different, determine from the communication to alter behavior of the multi-tiered cache in response to the detected change, and adjust how caching is performed in the multi-tiered cache in response to the detected changes at the other tier, including adjusting a memory allocation size of the dynamically resizable cache element.

17. The storage subsystem of claim 11, wherein the controllers of the first and second tiers of cache are configured to adjust the caching size and policy by adjusting a memory allocation size of the dynamically resizable cache element.

18. An article of manufacture comprising a computer-readable storage medium having content stored thereon, which when accessed by a computing device causes the computing device to perform operations including:

detecting, by a cache device controller for a tier of the multi-tiered cache, a change of workload characteristics at the tier of the multi-tiered cache, where at least one of the tiers of the multi-tiered cache includes a dynamically resizable cache element, and wherein each tier is managed by a controller;

communicating the detected change of workload characteristics from the controller to a different controller of a different tier of the multi-tiered cache to cause the different controller to adjust its caching size and policy in response to the detected changes, including adjusting a memory allocation size of the dynamically resizable cache element;

receiving a communication by the controller of the tier of the multi-tiered cache from the controller of the different tier indicating detection by the controller of the different tier of a change of workload characteristics at the different tier when the controller of the different tier detects the change of workload characteristic;

determining from the communication to alter behavior of the multi-tiered cache in response to the detected change of workload characteristics; and

adjusting how caching is performed in the multi-tiered cache in response to the detected changes at the different tier.

19. The article of manufacture of claim 18, wherein detecting the change of workload characteristics comprises detecting one or more of a change in rate of cache miss, ratio of read versus write input/output (I/O) requests, I/O size, or ratio of random to sequential accesses.

20. The article of manufacture of claim 18, wherein to adjust the caching size and policy comprises changing a pre-fetch policy indicating an amount of read-ahead to perform, or changing a caching policy indicating how tong to keep data.

21. The article of manufacture of claim 18, wherein to cause the controller of the different tier to adjust caching size and policy comprises to adjust caching size and policy in response to the detected changes only if the detected changes are changed by more than a preconfigured threshold.

22. The article of manufacture of claim 18, wherein adjusting the caching size and policy comprises adjusting the caching size and policy by de-provisioning a virtual storage appliance acting as a tier of dynamic cache to remove at least a portion of a tier of the multi-tiered cache, or by dynamically instantiating a virtual storage appliance as a tier of dynamic cache to increase at least a portion of a tier of the multi-tiered cache.

23. The article of manufacture of claim 18, wherein adjusting the caching size and policy comprises adjusting a memory allocation size of the dynamically resizable cache element.