Method and apparatus for increasing the accuracy of predicting future IO operations on a storage system
A method of increasing the accuracy of predicting future IO operations on a storage system includes creating a snapshot of a production volume, linking the snapshot to a thin device, mounting the thin device in a cloud tethering subsystem, and tagging the thin device to identify the thin device as being used by the cloud tethering subsystem. When data read operations are issued by the cloud tethering subsystem on the tagged thin device, the data read operations are executed by a front-end adapter of the storage system to forward data associated with the data read operations to a cloud repository. The cache manager, however, does not use information about data read operations on tagged thin devices in connection with predicting future IO operations on the cache, so that movement of snapshots to the cloud repository do not skew the algorithms being used by the cache manager to perform cache management.
1. A method of increasing the accuracy of predicting future IO operations on a storage system, comprising the steps of:
receiving first data read operations from host computers by a front-end adapter of the storage system;
implementing the first data read operations by the front-end adapter, each respective first data read operation being implemented by the front-end adapter by locating data requested by the respective first data read operation in a shared cache or moving the data requested by the respective first data read operation from storage resources of the storage system to the shared cache, reading the respective requested data by the front-end adapter from the cache to the respective host computer, and reporting the cache read operation by the front-end adapter to a cache manager;
creating a snapshot of a production volume on storage resources of the storage system;
linking the snapshot to a thin device;
mounting the thin device in a cloud tethering subsystem;
tagging the thin device to identify the thin device as being used by the cloud tethering subsystem in connection with movement of the snapshot to a cloud repository;
issuing second data read operations, by the cloud tethering subsystem, on the tagged thin device;
executing the second data read operations by the front-end adapter of the storage system to forward data associated with the second data read operations to the cloud repository each second data read operation comprising locating the respective requested data in the shared cache or moving the respective requested data from the storage resources to the shared cache, reading the requested data by the front-end adapter from the cache, and reporting the cache read operation by the front-end adapter to the cache manager;
determining cache read operation access patterns on the cache of the storage system by the cache manager from reported cache read operations from the front-end adapter associated with the first data read operations, the cache read operation access patterns being used by the cache manager to set cache policies governing management of the cache; and
determining, by the cache manager, that the second data read operations were issued on the tagged thin device, and not using reported cache read operations on the cache associated with the second data read operations on the tagged thin device, by the cache manager, in connection with determining the cache read operation access patterns, so that movement of snapshots to the cloud repository do not affect setting of the cache policies governing the management of the cache.
2. The method of claim 1 , further comprising not including, by a compression subsystem, the data associated with the second data read operations in an uncompressed data pool of the storage system.
3. The method of claim 2 , further comprising a step of determining, by the compression subsystem, whether one of the second data read operations is on a tagged thin device prior to the step of not including the data associated with the second data read operations in the uncompressed data pool.
4. The method of claim 1 , wherein the snapshot has data stored on backend allocations of tracks of memory, and wherein the thin device is defined such that tracks of the thin device contain pointers to the backend allocations of the tracks of memory of the snapshot.
5. The method of claim 1 , wherein the snapshot has data stored on backend allocations of tracks of memory, and wherein the thin device is undefined such that tracks of the thin device do not contain pointers to the backend allocations of the tracks of memory of the snapshot.
6. The method of claim 5 :
wherein the step of executing the second data read operations by the front-end adapter of the storage system comprises issuing a respective request, for each second data read operation, to a data services subsystem to resolve the data address associated with the respective second data read operation.
7. The method of claim 6 , further comprising sending, by the data services subsystem, a request to a snapshot subsystem for a one time on-demand definition of a requested track of the thin device associated with the respective second data read operation.
8. The method of claim 7 , further comprising receiving, by the data services subsystem, a response from the snapshot subsystem, with a data track number where the requested data resides on the storage system.
9. The method of claim 8 , further comprising allocating a slot in the cache, by the data services subsystem, and copying the requested data from the data track where the requested data resides on the storage system to the allocated slot in the cache.
10. The method of claim 9 , further comprising forwarding, by the front-end adapter, the requested data from the allocated slot in the cache to the cloud repository.
11. The method of claim 1 , further comprising issuing data write operations, by the cloud tethering subsystem, on a second thin device, the data write operations being associated with movement of a second snapshot from the cloud repository to the storage system.
12. The method of claim 11 , further comprising using the data write operations, by the cache manager, in connection with determining write operation access patterns on the storage system, the write operation access patterns being used by the cache manager in connection with the read operation access patterns to set cache policies governing management of the cache.
13. The method of claim 11 , further comprising including, by the compression subsystem, the data associated with the data write operations in an uncompressed data pool of the storage system.