[ClusterLabs] DRBD or SAN ?

Digimer lists at alteeve.ca
Tue Jul 18 12:17:09 EDT 2017

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).

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