[ClusterLabs] DRBD or SAN ?

[Digimer]

On 2017-07-18 10:34 AM, Lentes, Bernd wrote:
> 
> 
> ----- On Jul 17, 2017, at 11:51 AM, Bernd Lentes bernd.lentes at helmholtz-muenchen.de wrote:
> 
>> Hi,
>>
>> i established a two node cluster with two HP servers and SLES 11 SP4. I'd like
>> to start now with a test period. Resources are virtual machines. The vm's
>> reside on a FC SAN. The SAN has two power supplies, two storage controller, two
>> network interfaces for configuration. Each storage controller has two FC
>> connectors. On each server i have one FC controller with two connectors in a
>> multipath configuration. Each connector from the SAN controller inside the
>> server is connected to a different storage controller from the SAN. But isn't a
>> SAN, despite all that redundancy, a SPOF ?
>> I'm asking myself if a DRBD configuration wouldn't be more redundant and high
>> available. There i have two completely independent instances of the vm.
>> We have one web application with a databse which is really crucial for us.
>> Downtime should be maximum one or two hours, if longer we run in trouble.
>> Is DRBD in conjuction with a database (MySQL or Postgres) possible ?
>>
>>
>> Bernd
>>
> 
> Is with DRBD and Virtual Machines live migration possible ?
> 
> 
> Bernd

yes, but dual-primary is needed (this is how the Anvil! does live
migration). With DRBD 9, you can set it up to momentarily do
dual-primary to support live migration, though I have not used this
myself yet.

With dual-primary, you need to be sure a few things are in place (ie:
proper fencing, but you need that anyway, a cluster resource manager, etc).

-- 
Digimer
Papers and Projects: https://alteeve.com/w/
"I am, somehow, less interested in the weight and convolutions of
Einstein’s brain than in the near certainty that people of equal talent
have lived and died in cotton fields and sweatshops." - Stephen Jay Gould