[Xen-API] xcp SR and drbd

[Denis Cardon <denis.cardon@xxxxxxxxxxxxxxxxxxxxxx>]

Hi everyone,

I'm wondering if it could be possible to extend lvm SR to integrate a 
DRBD primary/secondary redundancy for a two nodes installation.
Let me explains the context and the a possible solution.

we've been using drbd for some years on iscsi SAN with Xen/XCP, having 2 
redundant iscsi SAN and 2 Xen/XCP nodes.
This kind of setup works great, however for smaller setups it is kind of 
overkill.
So we started to integrate drbd directly on XCP nodes (there are some 
docs at linbits about it). However being a little bit paranoid about 
split brain scenario, we have always been using primary/secondary setups 
(SR1 primary on XCP1 and SR2 primary on XCP2).
This kind of setup has a big drawback : VMs with VDI on SR1 have to run 
on XCP1 and VMs with VDI on SR2 have to run on XCP2. There is a loss of 
flexibility and a loss of transparancy for XCP admins.
So I'd want to extend the lvm SR to integrate DRBD primary secondary, 
and I'd like to have some input on this kind of scenario :
* one each lvm, create a drbd resource, and when a vbd is brough up the 
drbd resource is switch to primary.
* when migrating a vm to the second node, turn drbd on first node 
secondary, turn drbd on the second node primary, and get on with 
resuming the VM.
* when a VMs is brought down, pbd is brought down and drbd resource is 
switch to secondary.
That would make a lot of drbd resource when accounting for snapshot and 
all, but if it could be possible to be done, it would be a tremendous 
addition for smaller setups for SMBs.
I'd be glad to have some input from the dev if possible. By the way, 
kudos to the devs for XCP 1.6, it really rocks.
Cheers,

Denis



--
Denis Cardon
Tranquil IT Systems
Les Espaces Jules Verne, bâtiment A
12 avenue Jules Verne
44230 Saint Sébastien sur Loire
tel : +33 (0) 2.40.97.57.55
http://www.tranquil-it-systems.fr


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