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AlwaysOn sometimes becomes out of sync


AlwaysOn sometimes becomes out of sync

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michael.mcloughlin
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I have upped the session time-out to 15 seconds, i assume this is just a standard ping?

Will see how it goes over the weekend.
HowardW
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michael.mcloughlin (1/31/2014)
I have upped the session time-out to 15 seconds, i assume this is just a standard ping?

Will see how it goes over the weekend.


Careful with that, it really depends what your priority is. Would you rather have your secondary get temporarily out of date, or have your primary hang for 15 seconds when this happens?

Microsoft documentation refers to it as a ping, however I doubt it's an ICMP packet, it'll be a specific heartbeat communication from the Windows Cluster services...
Perry Whittle
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HowardW (1/31/2014)
michael.mcloughlin (1/31/2014)
I have upped the session time-out to 15 seconds, i assume this is just a standard ping?

Will see how it goes over the weekend.


Careful with that, it really depends what your priority is. Would you rather have your secondary get temporarily out of date, or have your primary hang for 15 seconds when this happens?

Microsoft documentation refers to it as a ping, however I doubt it's an ICMP packet, it'll be a specific heartbeat communication from the Windows Cluster services...

Exacto mundo and should ideally have a separate network for the heartbeat traffic. Currently all traffic is pushed down the "same pipe"

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michael.mcloughlin
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Thanks guys, apologies if this sound daft but im the perfect example of the accidental DBA. Having come from a job with no exposure to clulstering and SQL (previous job was in schools) im still working this out in my head.

I have 3 network cards on the VMs all connected to different distributed switches which are tagged on different VLANs. How do i go about using a different network for the heartbeat as i cannot see anything related to this on the existing virtual cluster and physical cluster, only the public and 2 private iSCSI vlans are listed in failover manager.

From what i read when looking into this it is suggested that a heartbeat isn't required any more from SQL 2008 onwards? If this isn't recommended would another network card on each server on the same VLAN configured with a private IP (192.x.x.x for example) be enough for the heartbeat? obviously this would be set to Cluster use only?
Perry Whittle
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michael.mcloughlin (1/31/2014)
From what i read when looking into this it is suggested that a heartbeat isn't required any more from SQL 2008 onwards?

Yes but when running the cluster validation the report will still bleat about not having a separate network!


michael.mcloughlin (1/31/2014)
If this isn't recommended would another network card on each server on the same VLAN configured with a private IP (192.x.x.x for example) be enough for the heartbeat? obviously this would be set to Cluster use only?

A separate network would be advisable as you only have 1 Nic available

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michael.mcloughlin
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OK im getting mixed messages on whether a heartbeat network is needed, Microsoft recommend you dont use one for 2008 onwards as it can have adverse effects. I can get another VLAN created and add another NIC to the servers but if Microsoft say it isnt needed then why bother? Surely a 10GB interface should be able to handle a simple heartbeat between nodes?
Perry Whittle
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michael.mcloughlin (2/3/2014)
OK im getting mixed messages on whether a heartbeat network is needed, Microsoft recommend you dont use one for 2008 onwards as it can have adverse effects.

A lot changed in Windows 2008, Teamed adapter support was better as well as the improvements to the heartbeat networking. This post gives excellent detail of the changes.
The detail in the link above mentions the special virtual heartbeat adapter which uses an APIP address, thing is it will have to bind itself to a NIC on the server to be able to complete the heartbeat communication.


michael.mcloughlin (2/3/2014)
Surely a 10GB interface should be able to handle a simple heartbeat between nodes?

Yes but this 10Gbps connection is shared by however many VMs are connecting through the vSwitch, or are you saying that this VM is the only VM communicating through that switch?

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michael.mcloughlin
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Currently there are only these nodes with 10GBPs interfaces on this vSwitch. Any other VMs on the same vSwitch have 1Gbps nics configured. I will take a look at the URl you gave later, currently sorting a failed disk in the san Cool
Perry Whittle
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what version ESX\VSphere you using?

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JoseM
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Hi gurus !!

Check if you have any error in the SQL Server Errologs related with avaliable workers and raise the value in case you find this error.

How many databases you have using AlwaysON ? I plan tor prepare an 5000 databases AlwaysOn setup and my first tests ended with a bad result due a lack of threads. I increased the maximum workers value and it didn't help. Any of you have any experience with this amount of databases ? My understand is that it won't work with the hardware I have avaliable ( Two 16 corees 65 Gb of RAM ).

Check this table (The number of workers might vary depending the number of cores you have).

http://msdn.microsoft.com/en-us/library/ms190219.aspx
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