Mirroring v/s Clustering

Question

Hi All,

I have requirement i need to tell one of our client that things to consider for mirroring and clustering.

in that i need to provide

1)why should we use mirroring over clustering?

2)why should we use clustering over mirroring ?

3)Minimal configuration required for mirroring and clustering(RAM,CPU,STORAGE,STORAGE TYPE)?

4)How much down time clustering can maximum have?

5)How much down time Mirroring can maximum have?

6)Cost effective mirroring over clustering and vice versa??

7)Which one bears more load mirroring or clustering?

8)Availability??

9)any addition features which i left?

Thanks in advance

please help

Answer 1

1)Mirroring can be implemented in different geographic locations, Clustering is not possible Both the nodes must be in same geographic location

2)Fast recovery time comparedd with mirrorinf

3)Both( Principle and Mirrored must be with dame configuration of SQL Server Edition and every thing

4)5min

5)2-20 sec

6)Cost effective mirroring over clustering and vice versa??

7)clustering

8)Mirroring and clustering are high availability options

9)any addition features which i left?

---

Ramesh Babu Vavilla MCTS,MSBI

Answer 2

Hi Naik

Read below , these are quick ones and help you to answer ur client confidently

http://atdhebuja.wordpress.com/2011/03/01/benefits-advantages-of-database-mirroring-to-clustering/

http://ask.sqlservercentral.com/questions/1547/high-availibility-database-mirroring-or-clustering.html

Thanks

Saurabh Sinha

http://saurabhsinhainblogs.blogspot.in/

Please use Marked as Answer if my post solved your problem and use Vote As Helpful, if a post was useful to help other user's find a solution quicker

Answer 3

Thanks A lot for the answers

can you please tell me how fail-over happen in clustering??(in brief)

Answer 4

Hi

There is something called quorum which keep send and recive signals (heart beat signal) from active node in clustering, the moment quorum didnt recieve signal it send message to passive node  that Active node is down please wake upand behave as Active node. All cluster groups (resources) like drives .. move to node passive node and it starts working as active node (Sql server will start @ node2 now active).

Refrence link to study in detail : http://my.safaribooksonline.com/book/operating-systems-and-server-administration/virtualization/9780470572146/windows-clustering/how_failover_clustering_works

Thanks

Saurabh Sinha

http://saurabhsinhainblogs.blogspot.in/

Please use Marked as Answer if my post solved your problem and use Vote As Helpful, if a post was useful to help other user's find a solution quicker

Answer 5

Thanks a lot Saurabh,

In the same way can you please explain how mirroring fail-over works with witness in simple words as above?

Thanks in Advance

Answer 6

Hi,

Clustering with multiple servers that are configured to take over for one another when a failure occurs. The process of one server taking over for a failed server is commonly known as failover. A failover cluster is a set of servers that are configured so that if one server becomes unavailable, another server automatically takes over for the failed server and continues processing. Each server in the cluster has at least one other server in the cluster identified as its standby server.

For a standby server to become the active server, it must somehow determine that the active server no longer functions. The system usually uses one of the following general types of heartbeat mechanisms to accomplish this:

• Push heartbeats. For push heartbeats, the active server sends specified signals to the standby server at a well-defined interval. If the standby server does not receive a heartbeat signal over a certain time interval, it determines that the active server failed and takes the active role. For example, the active server sends a status message to the standby server every 30 seconds. Due to a memory leak, the active server eventually runs out of memory and then crashes. The standby server notes that it has not received any status messages for 90 seconds (three intervals) and takes over as the active server.

• Pull heartbeats. For pull heartbeats, the standby server sends a request to the active server. If the active server does not respond, the standby server repeats the request a specific number of times. If the active server still does not respond, the standby server takes over as the active server. For example, the standby server may send a getCustomerDetails message to the active server every minute. Due to a memory leak, the active server eventually crashes. The standby server sends the getCustomerDetails request three times without receiving a response. At this time, the standby server takes over as the active server

• For further detials

http://msdn.microsoft.com/en-us/library/ff650328.aspx

---

Please help and appreciate others by using these features: "Propose As Answer", "Vote As Helpful" and "Mark As Answer"

Waqas

MS(SPM), MS(E&F), MCP, MCT, MCTS, MCITP, MCSE, MCPD, MCSD, MCDBA , Author
Twitter: @waqas8777
Linked In: http://www.linkedin.com/in/waqasm1

Answer 7

Hi

Lots of questions hmmmmmmmm......

 Mirroring have 3 modes   (high availability , high protection and high performance)

1. Only high availablity offers Auto failover similar to clustering. here heartbeat signal sender / reciever is witness server (this will be your physical server).  high availability is synchronus and that why  offer no data loss

2. High protection doesnt offer auto failover , Any dba can do it manuall again its synchronus so no dataloss

3. High Performance : manual failover , there could be data loss as this is asynchronus

Refrence link : http://weblogs.sqlteam.com/tarad/archive/2008/05/04/60585.aspx

Thanks

Saurabh Sinha

http://saurabhsinhainblogs.blogspot.in/

Please use Marked as Answer if my post solved your problem and use Vote As Helpful, if a post was useful to help other user's find a solution quicker

Answer 8

I think you forgot one option - multisite clusters.  You can build a cluster and use 3rd party replication (host or array based). The following chart shows some of the benefits of each type of solution.  The chart and articles reference AlwaysOn Availability Groups...but most of the same limitations apply in Database Mirroring as well.

This solution gives you the best of both worlds.  I wrote some articles on this topic here:

http://clusteringformeremortals.com/2009/09/15/step-by-step-configuring-a-2-node-multi-site-cluster-on-windows-server-2008-r2-%e2%80%93-part-1/

http://clusteringformeremortals.com/2009/10/07/step-by-step-configuring-a-2-node-multi-site-cluster-on-windows-server-2008-r2-%e2%80%93-part-3/

http://clusteringformeremortals.com/2013/01/05/clustering-sql-server-2012-on-windows-server-2012-step-by-step/

http://clusteringformeremortals.com/2012/11/09/how-to-overcome-the-limitations-of-sql-server-alwayson-availability-groups-sqlpass/

---

David A. Bermingham, MVP, Senior Technical Evangelist, SIOS Technology Corp