Automated space management for server flash cache

摘要

Techniques for automatically allocating space in a flash storage-based cache are provided. In one embodiment, a computer system collects I/O trace logs for a plurality of virtual machines or a plurality of virtual disks and determines cache utility models for the plurality of virtual machines or the plurality of virtual disks based on the I/O trace logs. The cache utility model for each virtual machine or each virtual disk defines an expected utility of allocating space in the flash storage-based cache to the virtual machine or the virtual disk over a range of different cache allocation sizes. The computer system then calculates target cache allocation sizes for the plurality of virtual machines or the plurality of virtual disks based on the cache utility models and allocates space in the flash storage-based cache based on the target cache allocation sizes.

主权项

1. A method for automatically allocating space in a flash storage-based cache, the method comprising:
collecting, by a computer system, an input/output (I/O) trace log for each virtual machine in a plurality of virtual machines or each virtual disk in a plurality of virtual disks; determining, by the computer system, a cache utility model for each virtual machine or each virtual disk based on the I/O trace log for the virtual machine or the virtual disk, wherein the cache utility model defines an expected utility of allocating space in the flash storage-based cache to the virtual machine or the virtual disk over a range of different cache allocation sizes, and wherein determining the cache utility model comprises:
adding an output value of a spatial locality function for the virtual machine or the virtual disk to an output value of a temporal locality function for the virtual machine or the virtual disk to generate an intermediate sum, wherein the spatial locality function models a probability of a cache hit as a function of cache size, and wherein the temporal locality function models a probability of a cache hit as a function of time; andmultiplying the intermediate sum by:
a service time for a physical storage device associated with the virtual machine or the virtual disk; anda read/write ratio for the virtual machine or the virtual disk; calculating, by the computer system, target cache allocation sizes for the plurality of virtual machines or the plurality of virtual disks based on the cache utility models; and allocating, by the computer system, space in the flash storage-based cache based on the target cache allocation sizes.