Full Synchronization

[jeddyatcc]

Can anyone please explain the algorithm that forces a full sync? I'm using StarWind to virtualize over 140TB of data, so obviously this takes quite some time to full sync. Over the past year I have rebooted my Starwind boxes 6-10 times without ever having to do a full sync. This past weekend, we had a very bad thing happen, a power outage(including UPS failure) followed by a bluescreen so both systems were down. Once it was resolved, I marked the last known good server as synchronized and let the full sync happen. Once completed, I decided to run some updates and fix what possibly bluescreened. I confirmed after each reboot that the sync was completed and up to date. After the 3rd reboot StarWind decided to do a full sync. That said can you provide me with best practices for performing patches that require multiple reboots? I have the logs, but don't want to post them to a public forum, but when I tried to open a ticket, the website kept failing.

[Anatoly (staff)]

Hello!

Sorry to hear that you have faced the issue.

The Full synchronization is starting instead of Fast in next cases:
1)If HA device was configured to use write-back cache and one of the server was turned off not correctly (i.e. hard reset, power outage, etc);
2)If the writes on the disk errors were detected on the disk;
3)If the partner that should be the source of synchronization has the state another from "Synchronized";
4)If initial synchronization was interrupted due to any reason;
5)If the extension of the HA device was performed;
6)If the Partner that should be the source of synchronization gained "Synchronized" state after initiating "Mark as synchronized" command

In the rest of the cases the fast synchronization takes place.

Synchronization will not start automatically if:
1)If the writes on the disk errors were detected on the disk;

I hope that helped.

[kmax]

This an interesting question because I've noticed something similar (although much smaller amounts disk usage)....

Do you stop the Starwind service before you did the reboots or did you just restart the servers during the patching?

[jeddyatcc]

Normally I just reboot after confirming synchronization is completed. But we are changing that internally and our Write-Back caching usage. I understand the reasons for why this takes so long, but I have had 0 luck convincing management to let me use RAID 0, or RAID 1/10 due to the risks/expense of each of them. Our next expansion is going to be handled much differently(hopefully more SSD). I would like to repeat though, that we are very happy with the product and it's performance. Once we understood what causes a full sync, we have been able to avoid causing them too often. As long as you view the environment as 1 large 3 controller RAID5 array, it makes much more sense and is easier to explain to people. I'm hopeful that the SSD stuff in V8 will assist in alleviating some of these problems as well.

[Anatoly (staff)]

Well, our next version should have (and I`m 99% sure that it will) the performance booster for parity RAID, and I think it will be useful for you.