Tag Archives: storage

iSNS support coming soon for LIO in Fedora

target-isns recently was added to Rawhide, and will be in a future Fedora release. This add-on to LIO allows it to register with an iSNS server, which potential initiators can then query for available targets. (On Fedora, see isns-utils for both the server, and client query tools.) This removes one of the few remaining areas that other target implementations have been ahead of LIO.

Kudos and thanks to Christophe Vu-Brugier for writing this useful program!

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.

RHEL 7.2 has an updated kernel target

As mentioned in the beta release notes, the kernel in RHEL 7.2 contains a rebased LIO kernel target, to the equivalent of the Linux 4.0.stable series.

This is a big update. LIO has improved greatly since 3.10. It has added support for SCSI features that enable VMWare VAAI support, as well as data integrity (DIF), and significant iSER work, for those of you using Infiniband. (SRP is also supported, as well as iSCSI and FCoE, of course.)

Note that we still do not ship support for the Fibre Channel qla2xxx fabric. It still seems to be something storage vendors and integrators want, more than a feature our customers are telling us they want in RHEL.

(On a side note, Infiniband hardware is pretty affordable these days! For all you datacenter hobbyists who have a rack in the garage, I might suggest a cheap previous-gen IB setup and either SRP or iSER as the way to go and still get really high IOPs.)

Users of RHEL 7’s SCSI target should find RHEL 7.2 to be a very nice upgrade. Please try the beta out and report any issues you find of course, but it’s looking really good so far.

iSER target should work fine in RHEL 7.1

Contrary to what RHEL 7.1 release notes might say, RHEL 7.1 should be fine as an iSER target, and it should be fine to use iSER even during the discovery phase. There was significant late-breaking work by our storage partners to fix both of these issues.

Unfortunately, there were multiple Bugzilla entries for the same issues, and while some were properly closed, others were not, and the issues erroneously were mentioned in the release notes.

So, for the hordes out there eager to try iSER target on RHEL 7.1 and who actually read the release notes —  I hope you see this too and know it’s OK give it a go 🙂

New screencast: 10 New Features in LIO and targetcli

I posted a new screencast that talks about ten new ease-of-use features that are new in Fedora 18.

10 New Features in LIO and targetcli

  1. Easier storage->ACL setup
  2. Name shows up as LUN model name
  3. Tags for initiator aliases and grouping
  4. ‘info’ command
  5. IPv6 portal support
  6. WWNs normalized
  7. Only show HW fabrics that are present
  8. 10 previous configs saved
  9. More info in summary
  10. iSER support
  11. Better sorting

Using qla2xxx with LIO on Fedora

In addition to turning your Fedora 18 box into an iSCSI target, LIO also supports other SCSI transport layers (‘fabrics’), such as Fibre Channel, with the qla2xxx fabric.

The most crucial bit is to verify that the qla2xxx driver has initiator mode disabled — it should be operating in target mode only. You can check this with:

cat /sys/module/qla2xxx/parameters/qlini_mode

It should say ‘disabled’. If it doesn’t, create a file called /usr/lib/modprobe.d/qla2xxx.conf and put:

options qla2xxx qlini_mode=disabled

in it. Then, run ‘dracut -f’ to rebuild your initrd, and reboot.

Some of you may be wondering: why /usr/lib/modprobe.d instead of /etc/modprobe.d ? This is because qla2xxx is likely loaded from the kernel’s initial ramdisk (initrd), and dracut, the initrd building tool, omits “host-specific” settings in /etc/modprobe.d. While you’re mucking around, also make sure the firmware package for your qla device, such as ql2200-firmware or similar, is also installed.

targetcli won’t let you create a qla2xxx fabric if qlini_mode is wrong. Once it lets you create the qla fabric, you can add luns to it and grant access permissions to acls exactly in the same manner as the other LIO fabrics.

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.

Screencast: targetd and lsmcli

I’ve whipped up a short (7min) screencast on targetd and lsmcli, two new additions to Fedora 18. targetd glues together LVM and LIO to expose a remote API for configuring a system for a storage array role. lsmcli is part of libstoragemgmt, which provides a common way to manage storage arrays from multiple vendors.

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 🙂