A method of operating a computer system having a persistent storage device including a non-volatile memory and a long-term storage medium (302, 430), the long-term storage medium being alternately put into a mode where it is readable and writeable, and into a mode where it is not readable or writeable, the method comprising: utilizing a first portion of said non-volatile memory as a read cache and a write buffer for intermediate storage of data from read and write operations (520, 540) from and to said long-term storage medium in a mode where the long-term storage medium is not readable or writeable, and for flushing the write buffer data to the long-term storage medium and repopulating the read cache in a mode where the long-term storage medium is readable and writeable; utilizing a second portion of said non-volatile memory as a portion to which at least one logical sector address, LSA, of said long-term storage medium has been mapped by means of a command that receives a list of said at least one LSA, said command being from an operating system or application, wherein utilizing the second portion comprises: when said at least one LSA is written to, performing a write operation to the second portion of said non-volatile memory; and when said at least one LSA is read from, performing a read operation from said second portion of said non-volatile memory, wherein data in the second portion does not get flushed to the long-term storage medium, nor does the long-term storage medium provide data to the second portion, unless new LSAs are to be mapped to the second portion. utilizing a first portion of said non-volatile memory as a read cache and a write buffer for intermediate storage of data from read and write operations (520, 540) from and to said long-term storage medium in a mode where the long-term storage medium is not readable or writeable, and for flushing the write buffer data to the long-term storage medium and repopulating the read cache in a mode where the long-term storage medium is readable and writeable; utilizing a second portion of said non-volatile memory as a portion to which at least one logical sector address, LSA, of said long-term storage medium has been mapped by means of a command that receives a list of said at least one LSA, said command being from an operating system or application, wherein utilizing the second portion comprises: when said at least one LSA is written to, performing a write operation to the second portion of said non-volatile memory; and when said at least one LSA is read from, performing a read operation from said second portion of said non-volatile memory, wherein data in the second portion does not get flushed to the long-term storage medium, nor does the long-term storage medium provide data to the second portion, unless new LSAs are to be mapped to the second portion. when said at least one LSA is written to, performing a write operation to the second portion of said non-volatile memory; and when said at least one LSA is read from, performing a read operation from said second portion of said non-volatile memory, wherein data in the second portion does not get flushed to the long-term storage medium, nor does the long-term storage medium provide data to the second portion, unless new LSAs are to be mapped to the second portion.