mirror of
https://github.com/SCST-project/scst.git
synced 2026-05-17 10:41:26 +00:00
f59534735d
In testing SCST performance with MD RAID arrays for the backing device, and RHEL 7.x initiators generating I/O, with the current optimal transfer length (512 KiB) that SCST provides initiators (via the block limits VPD page), it was observed on the target side that partial stripe writes were occurring, even though at the file system layer full stripe writes were being generated. Through testing it was determined the "optimal_io_size" sysfs attribute and/or optimal transfer length data in the VPD page were being utilized to fragment I/O on the initiator side. While using the value of "optimal_io_size" from the MD RAID device (via sysfs) stops partial stripe writes, it was observed additional throughput can be gained by doubling/tripling/quadrupling this value. And it was also observed that different values were preferred for writes vs. reads to yield best performance. The default value is 512 KiB (524288 bytes). Signed-off-by: Marc Smith <marc.smith@parodyne.com> [bvanassche: Made opt_trans_len attribute read/write] git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@7856 d57e44dd-8a1f-0410-8b47-8ef2f437770f
Overview ======== This is the SCST development repository. It contains not a single project SCST as one can think, but a number of them, which are divided as the following: 1. SCST core in scst/ subdirectory 2. Administration utility for SCST core scstadmin in scstadmin/ 3. Target drivers in own subdirectories qla2x00t/, iscsi-scst/, etc. 4. User space programs in usr/ subdirectory, like fileio_tgt. 5. Some various docs in doc/ subdirectory. Those subprojects are in most cases independent from each other, although some of them depend from the SCST core. They put in the single repository only to simplify their development, they are released independently. Thus, use "make all" only if you really need to build everything. Otherwise build only what you need, like for iSCSI-SCST: make scst scst_install iscsi iscsi_install For more information about each subproject see their README files. QLogic target driver ==================== QLogic target driver qla2x00t is the old driver, forked from qla2xxx several years ago. It is very stable, well tested and actively used in many production setups. There is also new driver, maintained by QLogic, which, among other, supports 32G FC, see http://scst.sourceforge.net/target_qla2x00t.html. You can find the latest version of it in git://git.qlogic.com/scst-qla2xxx.git. To integrate it into the SCST build tree you need to clone the QLogic git tree in a subdirectory of this directory (SCST root tree) with name qla2x00t_git (or create a symlink with this name pointing to any other location in your system). Now common and QLA specific root Makefile targets "magically" start working with the new driver. Then follow instructions in the git's README. In presence of qla2x00t_git subdirectory you can still build the qla2x00t using qla_old* root Makefile targets. Vladislav Bolkhovitin <vst@vlnb.net>, http://scst.sourceforge.net