[Pacemaker] About SBD.

[Carlos Turiel]

Hi,

I'm using the SBD fencing method in my Career Final Project. I'm student
but work like linux sysadmin since years ago. :)

In Ubuntu Krusty, i don't find the package for bsd and the bsd software was
removed from cluster-glue package. Compile and install bsd was pretty hard
but it was done.

The sbd agent shows the follow information:

---

root at nodo1:/usr/lib/stonith/plugins/external
# ./sbd getinfo-devdescr
sbd uses a shared storage device as a medium to communicate
fencing requests. This allows clusters without network power
switches; the downside is that access to the shared storage
device becomes a Single Point of Failure.

It requires sbd to be configured on all nodes.

Please read http://linux-ha.org/wiki/SBD_Fencing!

---

I don't understand why the SBD method is a SPOF. If it use a SAN, the block
device can be in mirror RAID in the Storage. With multipath fibre gets
redundancy in the communications. Where would be the SPOF? it would be the
sbd daemon? it would be reasonable to run the bsd daemon like resource in
Pacemaker? I think controld agent resource might be right to run the bsd
daemon.

I think the I/O fencing is the best option because it doesn't depend of
network to be operative. It is SBD truely independent from network status
for work? I have my dudes because in the compilation of the binary, sbd
needs corosync and pacemaker libs.


Finally, IMHO, let me some suggestions to improve SBD.

It would be nice that by default, "sbd list", "sbd dump" and others commands
, would work without having to specify the device parameters. Of course, the
variable SBD_DEVICE in /etc/sysconfig/sbd file, would be defined.

---

root at nodo1:/usr/lib/stonith/plugins/external
# grep SBD_DEVICE /etc/sysconfig/sbd
# SBD_DEVICE specifies the devices to use for exchanging sbd messages
SBD_DEVICE="/dev/disk/by-id/ata-VBOX_HARDDISK_VB37c86fb9-b67e3db4-part1;/dev/disk/by-id/ata-VBOX_HARDDISK_VB24ac6909-20d73ce9-part1;/dev/disk/by-id/ata-VBOX_HARDDISK_VB051291f4-f95e847d-part1"
root at nodo1:/usr/lib/stonith/plugins/external
# sbd list
You must specify 1 to 3 devices via the -d option.
sbd failed; please check the logs.
root at nodo1:/usr/lib/stonith/plugins/external
# sbd -d /dev/disk/by-id/ata-VBOX_HARDDISK_VB37c86fb9-b67e3db4-part1 -d
/dev/disk/by-id/ata-VBOX_HARDDISK_VB24ac6909-20d73ce9-part1 -d
/dev/disk/by-id/ata-VBOX_HARDDISK_VB051291f4-f95e847d-part1 list
0       nodo2   clear
1       nodo1   clear
0       nodo2   clear
1       nodo1   clear
0       nodo2   clear
1       nodo1   clear

---

In debian and ubunut distros, the /etc/sysconfig directory doesn exist. The
directory equivalent would be /etc/defaults.

The initscript sbd is not compatible in debian distros. I modified the
provieded script to work in ubuntu and debian. I don't know if that would
be task for the debian HA maintainers.

I think that the initscript should be load the softdog module in the start
function if the parameter is defined.


One last question. Which is the official repository and website of the SBD
proyect?
- http://linux-ha.org/wiki/SBD_Fencing
- https://github.com/l-mb/sbd/
- http://hg.linux-ha.org/sbd/


Thank you so much!

A great and cool software, Corosync, Pacemaker and SBD.


Saludos.
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