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Selectively reading data from cache and primary storage based on whether cache is overloaded

  • US 10,430,338 B2
  • Filed: 01/21/2010
  • Issued: 10/01/2019
  • Est. Priority Date: 09/19/2008
  • Status: Active Grant
First Claim
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1. A method comprising, during a period in which an intermediate cache is already storing a copy of a particular item and a particular cache is not storing the particular item:

  • receiving an I/O request at a storage system, from a database server executing in a computer system that includes volatile memory;

    wherein the volatile memory has at least a portion that is used as the particular cache;

    wherein the I/O request is to retrieve, for a scan operation being performed by the database server, a plurality of items that includes the particular item;

    wherein the particular item resides on persistent primary storage managed by the storage system;

    wherein the intermediate cache, managed by the storage system, is logically positioned between the volatile memory of the computer system and the persistent primary storage;

    in response to receiving the I/O request, the storage system performing the steps of;

    determining whether to service the I/O request with the copy of the particular item that resides in the intermediate cache based on one or more factors, wherein the one or more factors include at least one of;

    an identity of a user for whom the I/O request was submitted,an identity of a service that submitted the I/O request,an indication of a consumer group to which the I/O request maps,whether the I/O request is associated with an offloaded filter provided by the database server to the storage system, orwhether the intermediate cache is overloaded;

    in response to determining, based on the one or more factors, that the I/O request should be serviced with the copy of the particular item that resides in the intermediate cache, responding to the I/O request with the copy of the particular item that resides the intermediate cache without retrieving the particular item from primary storage;

    wherein the storage system applies filter criteria, provided to the storage system by the database server, to items involved in the scan operation; and

    wherein the method is performed by one or more computing devices.

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