Planning Stretch Cluster build : Storage questions for HA

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Hello,

I am trying to design a Redhat Enterprise Linux Stretch cluster which will consist of 2 or more VMWare virtual machines. The machines will live on hosts that are in two different COLO's inside of a large datacenter.

Each VMware host will be able to access the same compute, storage, and networking resources.

My question is in regards to the shared disk that the two or more VM's will need to use for the cluster. I was wondering if I could provision an iSCSI LUN from one array in each COLO , then use LVM on each VM to mirror the iSCSI disks in a Logical Volume . I am hoping this works , so we can have redundancy in the event that connectivity to a storage array was lost.

Would this scenario work, or would LVM not work between two different nodes?

Or is there a better way to ensure that the data is highly available and synchronized real-time ?

Thank you,

Responses

Just found out this question, have you checked https://access.redhat.com/articles/27136 for Information about Stretch Clusters?

Regarding storage, usually one source is provided, or if there are two ones, some method should be used to ensure that only one node has access to it at a time for example HA-LVM with tags (not clvmd based).

I would recommend you to file a support case for this to be tracked properly.

Regards, Pablo

Yes, as Pablo said you may fill a support case for architecture review by Red Hat.

Ability to access shared logical volumes could be achieved by using "clvmd" wherein all nodes could access the storage provided it is cluster aware application or file system, OR using HA-LVM wherein a single node would access storage at any given time. '

Look at this snip from Red Hat Cluster guide:

When to use CLVM or HA-LVM should be based on the needs of the applications or services being
deployed.

If the applications are cluster-aware and have been tuned to run simultaneously on multiple
machines at a time, then CLVM should be used. Specifically, if more than one node of your cluster
will require access to your storage which is then shared among the active nodes, then you must
use CLVM. CLVM allows a user to configure logical volumes on shared storage by locking access
to physical storage while a logical volume is being configured, and uses clustered locking
services to manage the shared storage. For information on CLVM, and on LVM configuration in
general, refer to Logical Volume Manager Administration.

If the applications run optimally in active/passive (failover) configurations where only a single
node that accesses the storage is active at any one time, you should use High Availability Logical
Volume Management agents (HA-LVM).

Plan a storage array which could be easily accessible from either side of your clustered nodes.

Check out this KB : https://access.redhat.com/solutions/3067

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