[ClusterLabs] DRBD or SAN ?

Digimer lists at alteeve.ca
Mon Jul 17 13:30:29 EDT 2017

On 2017-07-17 05:51 AM, Lentes, Bernd 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

DRBD any day.

Yes, even with all the redundancy, it's a single electrical/mechanical
device that can be taken offline by a bad firmware update, user error,
etc. DRBD gives you full mechanical and electrical replication of the
data and has survived some serious in-the-field faults in our Anvil!
system (including a case where three drives were ejected at the same
time from the node hosting the VMs, and the servers lived).

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