[pve-devel] [PATCH storage 0/2] Add SCST provider to ZFS over iSCSI

Дмитрий Котиков dkotsikau at gmail.com
Thu May 3 20:01:07 CEST 2018


ISER and srpt are not supported by libiscsi that comes with Proxmox.  It
can be built with ISER support, but Debian version comes without it, it is
old one.
Thus qemu is also built with old libiscsi and does not support iSER and
srpt. I tried to switch SCST to iSER and found out that I could not do it
without deployment of the new libiscsi and rebuilding of QEMU stuff.

I tried several years ago to use LIO. My ESXi hosts did not work with it.
Also there were issues with clusters when I tried to use LIO for them.
So the only thing that worked at that time was SCST.

When I had to select LIO or SCST I found out that LIO was renamed to TCM,
and I had no idea what was changed. So SCST was the olny iSCSI target that
worked in my memory.

I also had to ask SCST team to resolve some issues with scstadmin tool to
fix an issue with LUN deletion. There are my e-mails in their dev stream.
Also SCST team added dpkg target to makefile to build deb packages several
months ago.
Only after that I decided to submit SCST patches to Proxmox team. I just
had to re-apply  patch after every Proxmox update. It works on my server
alredy for 4 months and I have decided to make things easier. :)

SCST and QEMU have some incompabilities. If block size is not 512 in SCST,
then qemu-img will fail with very odd message. It fails to calculate
correct size of the disk.
So SCST is not ideal (or qemu - I haven't found which one fails and to what
team I should report a defect), but it works at least.

In my understanding, the topic is not why SCST  is better/worse than LIO.
The topic is that SCST support is now added in Proxmox somehow, but LIO is
not.
Someone else can try to add LIO support to Proxmox.

чт, 3 мая 2018, 19:35 Dietmar Maurer <dietmar at proxmox.com>:

> > dkms packages run fine, and scst is imho the most prferrable target
> > available.
>
> DKMS is a PITA
>
> and LIO drivers are include by default
> > In special when it comes to ease of management via sysfs and support for
> > rdma transports like iser and srp.
> >
> > Also, the target not necessary runs on the PVE host itself but could be
> > either virualized or on a separate host / san
>
> Yes, so why not use the iSCSI target included in any Linux distribution?
>
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