On Fri, 2008-02-08 at 17:42 +0300, Vladislav Bolkhovitin wrote: > Nicholas A. Bellinger wrote: > > On Thu, 2008-02-07 at 12:37 -0800, Luben Tuikov wrote: > > > >>Is there an open iSCSI Target implementation which does NOT > >>issue commands to sub-target devices via the SCSI mid-layer, but > >>bypasses it completely? > >> > >> Luben > >> > > > > > > Hi Luben, > > > > I am guessing you mean futher down the stack, which I don't know this to > > be the case. Going futher up the layers is the design of v2.9 LIO-SE. > > There is a diagram explaining the basic concepts from a 10,000 foot > > level. > > > > http://linux-iscsi.org/builds/user/nab/storage-engine-concept.pdf > > > > Note that only traditional iSCSI target is currently implemented in v2.9 > > LIO-SE codebase in the list of target mode fabrics on left side of the > > layout. The API between the protocol headers that does > > encoding/decoding target mode storage packets is probably the least > > mature area of the LIO stack (because it has always been iSCSI looking > > towards iSER :). I don't know who has the most mature API between the > > storage engine and target storage protocol for doing this between SCST > > and STGT, I am guessing SCST because of the difference in age of the > > projects. Could someone be so kind to fill me in on this..? > > SCST uses scsi_execute_async_fifo() function to submit commands to SCSI > devices in the pass-through mode. This function is slightly modified > version of scsi_execute_async(), which submits requests in FIFO order > instead of LIFO as scsi_execute_async() does (so with > scsi_execute_async() they are executed in the reverse order). > Scsi_execute_async_fifo() added as a separate patch to the kernel. The LIO-SE PSCSI Plugin also depends on scsi_execute_async() for builds on >= 2.6.18. Note in the core LIO storage engine code (would be iscsi_target_transport.c), there is no subsystem dependence logic. The LIO-SE API is what allows the SE plugins to remain simple and small: -rw-r--r-- 1 root root 35008 2008-02-02 03:25 iscsi_target_pscsi.c -rw-r--r-- 1 root root 7537 2008-02-02 17:27 iscsi_target_pscsi.h -rw-r--r-- 1 root root 18269 2008-02-04 02:23 iscsi_target_iblock.c -rw-r--r-- 1 root root 6834 2008-02-04 02:25 iscsi_target_iblock.h -rw-r--r-- 1 root root 30611 2008-02-02 03:25 iscsi_target_file.c -rw-r--r-- 1 root root 7833 2008-02-02 17:27 iscsi_target_file.h -rw-r--r-- 1 root root 35154 2008-02-02 04:01 iscsi_target_rd.c -rw-r--r-- 1 root root 9900 2008-02-02 17:27 iscsi_target_rd.h It also means that the core LIO-SE code does not have to change when the subsystem APIs change. This has been important in the past for the project, but for upstream code, probably would not make a huge difference. --nab - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
