Thanks for your reply Robert, exactly what I'm thinking, but, my
management team directives are clear : no baremetal, I have to use only
cloud solution.
I'm aware of solution as Minio or Ceph, but, I'm very interested by
DRBD, looks like a strong technology. We have two use cases :
1 - Storage of about 5GB of small files (10kb in average) that are
written and read very often.
2 - Archive storage (2TB) of files size from 10kb to 10+ Mb , write and
read are more rare and higher latency is not a problem.
I'm trying to set up a test environment, I'm using Ubuntu server as
distribution, is that a correct choice ? Or Red Hat based distrib would
be easier to work with ?
Also, it's not clear how to make the link between GFS, Corosync /
Pacemaker and DRBD. Where could I find some good doc to understand what
I'm doing ?
Best,
Jérôme
Le 18/03/2020 à 11:49, Robert Altnoeder a écrit :
On 18 Mar 2020, at 09:15, Jérôme Barotin <[email protected]> wrote:
Hi,
I'm considering installing DRBD to share a filesystem in real time between two
different cloud provider (OVH & Hetzner average ping 20ms).
Both of them provide CEPH based block storage, my idea is to synchronize a 2/3
TB sized partitions, ideally with the DRDB with protocol C in an active /
active configuration.
Do you think it's possible ?
It is about as possible as it is possible to walk through a minefield and
survive. It is possible, but it is not something anyone should atttempt.
Sharing a filesystem across multiple nodes requires a cluster filesystem, which
requires distributed locking and also requires a dual-primary DRBD with a
high-reliability replication link and reliable fencing, because any
interruption of the link causes an immediate split-brain situation otherwise -
also including virtual machines not answering in time, and that is also a
common problem in cloud environments, because there are no scheduling
guarantees and the cloud hypervisors are often highly overprovisioned.
So to summarize, virtually everything in a multi-site cloud environment is the
worst case scenario for a high availability cluster, especially one with a
cluster filesystem, and it would probably provide higher availability to run no
cluster at all (just a single machine) and fail over manually as required than
trying to run a dual-primary shared-filesystem cluster across multiple cloud
environments.
Also, DRBD on top of Ceph doesn’t sound too right in the first place. That’s
like running a Linux VM in a Windows VM on a Linux hypervisor, when you are
really just using a single Linux instance.
So long story short, not recommended.
However, if you could tell us what use case you are actually trying to realize,
we might be able to suggest a setup that does the job.
br,
Robert
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