Tag Archives: rtslib

Some targetcli and TCMU questions

Just got an email full of interesting questions, I hope the author will be ok with me answering them here so future searches will see them:

I searched on internet and I don’t find some relevant info about gluster api support via tcmu-runner. Can you tell me please if this support will be added to the stable redhat targetcli in the near future? And I want to know also which targetcli is recommended for setup (targetcli or targetcli-fb) and what is the status for targetcli-3.0.

tcmu-runner is a userspace daemon add-on to LIO that allows requests for a device to be handled by a user process. tcmu-runner has early support for using glfs (via gfapi). Both tcmu-runner and its glfs plugin are beta-quality and will need further work before they are ready for stable Fedora, much less a RHEL release. tcmu-runner just landed in Rawhide, but this is really just to make it easier to test.

RHEL & Fedora use targetcli-fb, which is a fork of targetcli, and what I work on. Since I’m working on both tcmu-runner and targetcli-fb, targetcli-fb will see TCMU support very early.

The -fb packages I maintain switched to a “fbXX” version scheme, so I think you must be referring to the other one 🙂 I don’t have any info about the RTS/Datera targetcli’s status, other than nobody likes having two versions, the targetcli maintainer and I have discussed unifying them into a common version, but the un-fun work of merging them has not happened yet.

tgtd -> LIO kernel target in RHEL 7

RHEL 7 will be using the LIO kernel target subsystem for iSCSI and other protocols, instead of the tgtd daemon, aka scsi-target-utils. This is a change from RHEL 6, where we use tgtd for iSCSI target support, and LIO only for FCoE targets, via the fcoe-target-utils package.

Users of tgtd can prepare for RHEL 7 by trying Fedora 17 or 18, which have current LIO/targetcli code. LIO has many features tgtd doesn’t, but LIO also won’t cover 100% of tgtd’s features at first, either. File bugs for these regressions and we’ll work to address them.

Other software that currently uses tgtd may wish to look at the rtslib Python library, and targetcli’s JSON config format — LIO has a nice API so if you find yourself wanting to parse targetcli output, please hold off and email me instead, ok? 🙂

scsi-target-utils will still be available via EPEL for RHEL 7, and supported in RHEL 6 for its lifetime.

python-kmod will be in Fedora 18

python-kmod is a basic Python wrapper around the kmod library. It allows you to load, unload, and view Linux kernel modules without resorting to the subprocess module.

If you have Python code that works with kernel modules, please consider using this library in the future. If you have C code that works with modules, you should use libkmod directly! As I’ll be talking about at this years LPC, proper libraries are preferable to calling cmdline progams for low-level stuff, and now there’s one less reason to do so.

Using python-kmod, python-rtslib (and thus targetcli and targetd) now work with no use of subprocess, although rtslib will fall back to modprobe via subprocess if python-kmod is not present.

Thanks to Jiri Popelka for reviewing the python-kmod package, sorry it took me so long to fix it up 🙂