Caching with flash-based memory

• US 8,583,865 B1
• Filed: 12/21/2007
• Issued: 11/12/2013
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Sade, Gilad, Linnell, Thomas E.
• Primary Examiner(s): Mackall, Larry
• Application Number:
  US12/004,992
• Time in Patent Office: 2,153 Days
• Field of Search: 711/103, 711/114, 711/E12.001, 711/E12.016
• US Class Current: 711/113
• CPC Class Codes: G06F 11/108 Parity data distribution in semiconductor storages, e.g. in SSD
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/0811 with multilevel cache hierarchies
• 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 2212/1016 Performance improvement
• CPC Class Codes: G06F 2212/225 Hybrid cache memory, e.g. having both volatile and non-volatile portions
• CPC Class Codes: G06F 2212/286 Mirrored cache memory
• CPC Class Codes: G06F 2212/313 In storage device
• CPC Class Codes: G06F 2212/7208 Multiple device management, e.g. distributing data over multiple flash devices

Abstract

A system is used in caching with flash-based memory. First and second controllers communicate with a flash-based cache. A magnetic disk array is in communication with the flash-based cache. The flash-based cache has a dual ported link to the first and second controllers. The flash-based cache has flash-based memory components arranged in a RAID data protection scheme.

Claims

1. A system for use in caching with flash-based memory, the system comprising:

first and second controllers communicating with a flash-based cache, wherein the first controller communicates with a first volatile memory cache and the second controller communicates with a second volatile memory cache; and

a magnetic disk array in communication with the flash-based cache;

wherein

the flash-based cache is in communication with the first and second volatile memory caches, wherein the flash-based cache serves as an extension of the first and second volatile memory caches by providing the flash-based cache for caching data in addition to the first and second volatile memory caches, wherein the flash-based cache represents a non-volatile portion of a cache subsystem of the system, wherein the cache subsystem includes the flash-based cache and the first and second volatile memory caches, wherein a write I/O from a host is acknowledged to the host as complete once the data from the write I/O has been copied to the flash based cache;

the flash-based cache has a dual ported link to the first and second controllers, wherein the dual ported link enables the first and second controllers to simultaneously access memory in the flash-based cache, wherein the dual ported link enables the first controller to continue accessing the memory in the flash-based cache upon failure of the second controller; and

the flash-based cache has flash-based memory components arranged in a RAID data protection scheme.

2. The system of claim 1, wherein the handling of host I/Os is partitioned, so that some of the host I/Os are processed using the volatile memory cache, and others of the host I/Os are processed using the flash-based cache.

3. The system of claim 1, wherein the flash-based cache is effectively its own vault in the event of power failure.

4. The system of claim 1, wherein the flash-based cache uses metadata describing how and when data is being used.

5. The system of claim 1, wherein the flash-based cache holds information that the system needs when the system boots up, before disks of the magnetic disk array are spun up.

6. The system of claim 1, wherein if a flash-based memory component fails, data integrity is maintained and the flash-based memory component can be replaced and its data can be rebuilt from the other flash-based memory components.

7. The system of claim 1, wherein if an application needs to access data in non-sequential locations on disks of the magnetic disk array, the data is loaded into the flash-based cache.

8. The system of claim 1, wherein the system causes an application'"'"'s dataset to be loaded into the flash-based cached in advance of processing by the application.

9. The system of claim 1, wherein the packaging of the first and second controllers excludes the flash-based cache.

10. The system of claim 1, wherein a portion of the flash-based cache is turned off if not needed, to conserve energy.

11. The system of claim 1, wherein a drive of the magnetic disk array is turned off once data from said drive is loaded into the flash-based cache.

12. The system of claim 1, wherein when a host communicating with the system switches executing applications, data related to a first application is flushed from the flash-based cache to the magnetic disk array, a disk of the magnetic disk array is turned off, and data related to a second application is loaded into the flash-based cache.

13. The system of claim 1, wherein both first and second controllers can simultaneously access all of the memory of the flash-based cache.