[DRBD-user] Suggestion for Storage-Plugin

Roland Kammerer roland.kammerer at linbit.com
Fri Sep 1 11:19:39 CEST 2017

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On Fri, Sep 01, 2017 at 09:57:36AM +0200, Frank Rust wrote:
> Hi all,
> I’m not sure, if this is the correct mailing list to make a suggestion for a new storage plugin (or an extension to the existing LVM-plugin).
> 
> I have nodes with 12 disks each creating the drbdpool volume group. This could give me the opportunity to create LVMs in stripes to get a higher overall throughput.
> 
> My very simple solution to get striped LVMs was to create a renamed copy of the lvm storage plugin (lvm12s.py), and simply modify the lvm creation command to
> 
>                   self._cmd_create, "--stripes", "12", "--stripesize", "64", "-n", lv_name, "-L", str(size) + "k",
> instead of
>                 self._cmd_create, "-n", lv_name, "-L", str(size) + "k",
> 
> and of course adding this to plugins.py and to the cluster config.
> 
> I would suggest to implement a flexible method to create such striped LVMs.

Yes, some general "optional flags" could do that. The problem is that if
you give users the possibility to do that, they use it ;-). See the
other threads where users decided to use one plugin this day and the
other plugin the next day, where putting a red-fire-alert-sign and
telling them exactly that this is not supported in the users guide does
not stop them... And we provide support to customers, and it really
makes it easier for us to start from a "defined set" and not from one
where they specified OPTS="`rm -rf mydata && echo 'but still complain'`" ;-)

That said, there are obviously cases where a more fine-grained control
would be good. The current incarnation of drbdmanage is pretty much in
frozen state and gets only bug fix releases, so it will not happen in
the drbdmanage as of now. "Forking" an existing plugin is the way to go
here...

Regards, rck



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