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Snapshot coordination

  • US 9,189,396 B2
  • Filed: 08/24/2012
  • Issued: 11/17/2015
  • Est. Priority Date: 08/24/2012
  • Status: Active Grant
First Claim
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1. A method, performed by one or more computing devices, comprising:

  • handling by a SAN array one or more control plane tasks related to connectivity and one or more snapshots;

    creating a logical unit number (LUN) on the SAN array;

    coupling communicatively a host cache to the SAN array, wherein non-data network communications between the SAN array and the host cache are used to manage the connectivity and coordinate one or more snapshot requests, wherein the non-data network communications comprises a virtual IP address interface;

    creating a cached LUN at the host cache, wherein the cached LUN represents the caching instance of the LUN across a plurality of servers;

    receiving at the host cache, a first request to prepare a volume of the host cache for creating a snapshot of the cached LUN wherein the first request indicates that a snapshot of the cached LUN will be taken;

    preparing, in response to the first request, the volume of the host cache for creating the snapshot of the cached LUN, wherein preparing the volume of the host cache is dependent on a mode of the host cache, wherein the mode of the host cache comprises at least one of write-through (WT), write-back (WB), or write-back-write-through (WB-WT) switching, and wherein preparing the volume comprises;

    flushing a set of data comprising at least one snapshot of the cached LUN when the host cache is in WB or WB-WT switching modes;

    switching the host cache to WT mode when the host cache is in WB-WT switching mode; and

    sending a message indicating that the volume is prepared for creating the snapshot of the cached LUN;

    receiving, at the host cache, a second request to create the snapshot of the cached LUN;

    in response to the second request, creating, at the host cache, the snapshot of the cached LUN;

    switching the host cache to WB mode when the host cache is in WB-WT switching mode;

    sending by the host cache a flush complete message to the SAN array to complete movement of the snapshot to the SAN array and to complete creation of the snapshot; and

    deleting by the cached LUN, the snapshot.

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