Figure 6 illustrates an example of this default way. In the example, the Redis NoSQL
store uses direct, application-level hardware operations on a VSIC mapped into its
virtual address space to access data on its own VSA. The VSA is provided by one of the
logical disks of the RAID controller. Within its VSA, Redis stores its local data, such as
its database and configuration. This makes sense because Redis can gain performance
benefits from directly accessing its own data. To allow other applications access to this
data, Redis exports appropriate filenames to the kernel-level VFS. This allows the text
editor in the example to open the configuration file. It does so by issuing an open system
call to the kernel specifying the fully qualified name of Redis’s configuration file. The
kernel returns a file descriptor that redirects the text editor to make all file access via
the POSIX interface of Redis’s application library that has direct accesses to the VSA