The invention provides an elastic or flexible SSD cache utilizing a hybrid RAID protocol combining RAID-0 protocol for read data and RAID-5 single parity protocol for write data in the same cache array. Read data may be stored in window sized allocations using RAID-0 protocol to avoid allocating an entire RAID stripe for read cache data. In the same SSD volume, dirty write data is stored in row allocations using RAID-5 protocol to provide single parity for the dirty write data. Read data is typically stored a window from the physical device having the largest number of available windows. Write data is stored in a row including the next available window in each arm, which decouples the window structure of the rows from the stripe configuration of the physical memory devices.