mhvtl虚拟带库官方介绍文档 Linux Virtual Tape Library.doc

Linux Virtual Tape Library License: GPL v2Q. Why GPL license.A. Because I like the idea of sharing.I dont profess to know everything (not even close). Having something I can share and allow others to share back is a good idea. Virtual Tape Library consists of several components. LLD - A low level driver implemented as a kernel module - mhvtl Target devices - Daemons vtltape(1) and vtllibrary(1) which implement SCSI target device(s) in user-space Utility commands mktape(1), vtlcmd(1) And startup scripts build_library_config(1), make_vtl_devices(1) The kernel module is based on the scsi_debug kernel module (http://sg.danny.cz/sg/sdebug26.html). mhvtl.ko is a pseudo HBA (LLD). Note: As of 0.16, there are no default devices. The support scripts will add Drives (SSC devices) library (SMC) depending on the contents of /etc/mhvtl/library_contents and /etc/mhvtl/device.conf. A char device back-end has been included with the vtl LLD driver This allows data and SCSI commands to be passed from the LLD to user-mode daemons (SCSI targets) which constently poll the driver and process any outstanding SCSI commands. vtltape vtltape(1) is the usermode SSC target daemon which writes/reads data to data files in the /opt/vtl directory (if a virtual tape has been loaded). The virtual tape files include a Medium Auxiliary Memory (MAM) data structure to store persistent data (number of tape loads, total data written/read, media type etc). vtllibrary vtllibrary(1) is the usermode SMC target daemon which reads its configuration from the file /etc/mhvtl/library_contents(5) at startup. The number of storage slots are built dynamically when the daemon starts. Hence changing the number of storage slots and media access slots are a matter of modifying the file contents and restarting the vtllibrary(1) daemon. All library commands are performed on data structures in memory ONLY. vtlcmd A utility vtlcmd(1) is used to administrator the daemons vtltape(1) and vtllibrary.Message queue (ke