Automatic HA device synchronization after the both nodes...

[anton (staff)]

1) Write back cache is recommended for production. Write-through is not going to help in this case anyway...

2) Putting both storage nodes down is assumed to be a DISASTER.

hmm i had a similar occurance to this occur the other week.

what happens then when you have HA running both have a hard crash, but because you run multipath and some servers are using the alt. path when you force bring up one node it causes massive issues because its not the most recent data for those using the alt path at the time ??

Steve

Hi, set write-through caching to avoid this failure!
Or use a filesystem on top that can tolerate errors.

Regards.

[gstephenson]

You're not expected to do what you're doing! You cannot bring one node up and use it for production. You need to bring up BOTH nodes, run a synchronization process between them and use full serviced cluster in production after that.

See it's only 50% probability (with 2 node config of course) you'll pick up yourself the node with the most recent version of your data.

hmm i had a similar occurance to this occur the other week.

what happens then when you have HA running both have a hard crash, but because you run multipath and some servers are using the alt. path when you force bring up one node it causes massive issues because its not the most recent data for those using the alt path at the time ??

Steve

But what about the new "mark as synchronized" feature in 5.8? Isn't that like running one node in production? Or is it safe because you automatically turn off write-back in that scenario? ...My setup is two-node hyper-v using failover cluster with HA (still on 5.7 though).

Graham

[anton (staff)]

1) "Mark as synchronized" is for scenarious when you've lost your partner once and forever (nuke strike for example). Then you pick-up last standing one, make it active, grab another freshly installed node and re-synchronize them @ the time first active one is feeding GPS maps to your cruise missiles.

2) It's safe as if cluster wents down active node stops doing write-back thing and reverts to write-thru one. With 3 node cluster (3-way synchronous replication between nodes) one node drop is not going to change anything BTW.

3) Your setup is fine. I'd upgrade to 5.8 however...

You're not expected to do what you're doing! You cannot bring one node up and use it for production. You need to bring up BOTH nodes, run a synchronization process between them and use full serviced cluster in production after that.

See it's only 50% probability (with 2 node config of course) you'll pick up yourself the node with the most recent version of your data.

hmm i had a similar occurance to this occur the other week.

what happens then when you have HA running both have a hard crash, but because you run multipath and some servers are using the alt. path when you force bring up one node it causes massive issues because its not the most recent data for those using the alt path at the time ??

Steve

But what about the new "mark as synchronized" feature in 5.8? Isn't that like running one node in production? Or is it safe because you automatically turn off write-back in that scenario? ...My setup is two-node hyper-v using failover cluster with HA (still on 5.7 though).

Graham