August 23, 2018 at 1:05 am
Hi
I am following these notes for always on install and have some basic queries:
For step 9
Click the Add… button to provide an IP address.
In the Add IP Address dialog box, enter your preferred virtual IP address in the IPv4 Address field.
Click OK. Click Next.
I presume I ask my network administrator to provide me with a dedicated IP address that will act as the virtual ip?
For step 10
In the Select Initial Data Synchronization page, select the Full option.
Provide a shared folder that is accessible to the replicas that the SQL Server service account used by both replicas has Write permissions to. This is just a temporary file share to store the database backups that will be used to initialize the
databases in an Availability group.
Can this file share folder be located on one of the always on servers? or should it be on a seperate server?
Also for the SQL Server service account used by both replicas, should this account ideally have admin writes to both servers, not have a password expiry date and not be my own user admin account?
thanks in Advance
August 23, 2018 at 3:24 am
The folder used for data synchronisation can be on either of the servers, yes. You don't need a third one.
For the service account you would ideally use a group Managed Service Account (the same one on both servers).
August 23, 2018 at 4:28 am
Thanks, and for the virtual IP ?
August 23, 2018 at 8:38 am
I ask our Windows team for that; it depends how things operate where you work.
August 24, 2018 at 5:24 am
Thanks Beatrix Kiddo for the replies.
Just one more query related to the 'witness forum' it seems always on is setup / configured to use this but in the install documentation its doesn't seem to be mentioned for failover cluster or always on installation.
August 25, 2018 at 10:19 am
caz100 - Friday, August 24, 2018 5:24 AMThanks Beatrix Kiddo for the replies.Just one more query related to the 'witness forum' it seems always on is setup / configured to use this but in the install documentation its doesn't seem to be mentioned for failover cluster or always on installation.
A witness is required for the cluster configuration - and will depend solely on how you want to configure your cluster. This is used to determine the cluster quorum - and the votes needed to insure the cluster is healthy.
For example - if you have 2 nodes in the cluster, each node would have 1 vote for quorum . A cluster needs to have more than 50% of quorum votes to be healthy (and alive) - so if you only have the 2 nodes and 2 votes and one node goes down then your cluster also goes down (1/2 is not *more* than 50%). To account for that scenario - a witness is created which can be either a disk witness or file share witness (with one vote). This means you now have 3 votes for quorum and if a node is down you still have 2 of 3 votes for quorum .
Now - if you have 3 nodes in the cluster you don't need a witness if all 3 nodes have a single vote. This configuration insures the cluster is healthy and available if a single node is down, but if 2 nodes are down at the same time the cluster will no longer be healthy and will be shut down. If you need to be able to have more than a single node outage in a 3-node cluster then you have to reconfigure quorum votes to allow for that scenario.
Neither AlwaysOn nor FCI care about the witness - the witness is solely to determine quorum in the cluster and whether or not the cluster is up and available (healthy).
Note: you can configure the node weight which affects the quorum vote for a specific node/witness. That is - you can set it up so a node has no weight - thus no vote - or more weight so it has a higher number of votes. A node with no weight (no vote) would allow for that node and one other node in the cluster to be down at the same time (as long as quorum is more than 50% with the remaining nodes and witness). An example of this would be a 3-node cluster with FCI across 2 nodes and AlwaysOn for the 3rd node where the AlwaysOn node is used for either reporting or DR and not HA. The 3rd node would be configured with no votes and a disk/file witness would be included to insure quorum is maintained.
Jeffrey Williams
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August 26, 2018 at 10:03 am
ok Thanks Jeffrey for explaining.
I didn't see it mentioned in this documentation hence was not sure if it was required:
http://mssqllover.blogspot.com/2017/03/step-by-step-configring-windows-fail.html
September 6, 2018 at 5:51 am
caz100 - Thursday, August 23, 2018 1:05 AMHi
I am following these notes for always on install and have some basic queries:For step 9
Click the Add… button to provide an IP address.
In the Add IP Address dialog box, enter your preferred virtual IP address in the IPv4 Address field.
Click OK. Click Next.I presume I ask my network administrator to provide me with a dedicated IP address that will act as the virtual ip?
For step 10
In the Select Initial Data Synchronization page, select the Full option.
Provide a shared folder that is accessible to the replicas that the SQL Server service account used by both replicas has Write permissions to. This is just a temporary file share to store the database backups that will be used to initialize the
databases in an Availability group.Can this file share folder be located on one of the always on servers? or should it be on a seperate server?
Also for the SQL Server service account used by both replicas, should this account ideally have admin writes to both servers, not have a password expiry date and not be my own user admin account?
thanks in Advance
the listener will need a unique virtual IP and a virtual computer object.
if you are not a domain administrator the VCO will need to be pre staged by an AD admin
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September 7, 2018 at 7:51 am
It feels like a good AlwaysOn/Windows clustering overview would do you well here, have you seen this AlwaysOn Stairway? http://www.sqlservercentral.com/stairway/112556/
And some other useful articles:
If you want to set up the windows luctser for AlwaysOn without being a Domain Admin, you need to follow this:
https://technet.microsoft.com/en-us/library/dn466519(v=ws.11).aspx
and
http://www.tech-coffee.net/alwayson-availability-group-wsfc-cluster-creation/
And info on a file share witness:
https://blogs.technet.microsoft.com/askpfeplat/2012/06/27/clustering-what-exactly-is-a-file-share-witness-and-when-should-i-use-one/
Hope these are of some use..
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