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Mirror vs. Cluster - Which should we do?


Mirror vs. Cluster - Which should we do?

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bhanf
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We have about 130 databases for clients and are looking for high avail.

In the next year we expect to double that.

We can afford about $60,000 in equipment.

The databases take up about 330 GB on HD now.

What would you do Mirroring or Cluster as the next step?

Right now we are log shipping and doing weekly backups to an off site location. I would not change that.
Lynn Pettis
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Since mirroring is done at the database level and clustering at the server level and you have a large number of databases; I'd go with clustering.

Cool
Lynn Pettis

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bhanf
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Thanks.

Could you expand on your reasons.
JeremyE
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Why not both?
It sounds like you are already log shipping to a secondary site. You could use clustering at your primary site and mirror to a stand alone server at your secondary site. This gives you a layer of HA with clustering and DR with mirroring.

Clustering is primarily for high availability and not disaster recovery unless you plan to geocluster/multisite cluster. You only have one set of data on disk.

Mirroring can be used for HA and DR if you have another site to mirror to. This gives you 2 copies of the data so if site 1 disappears you can run on site 2.
bhanf
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Edogg (4/9/2010)
Why not both?

Cost!!

Edogg (4/9/2010)

Clustering is primarily for high availability and not disaster recovery unless you plan to geocluster/multisite cluster. You only have one set of data on disk.


This is where we are confused - Why would anyone do Clustering at all?
SQLRNNR
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Clustering does provide a level of protection - even if you consider it just a High availability solution. It does cost more to implement than a standalone server, but you do get the benefit of uptime should a server fail.

Also, you can cluster servers that are in different buildings or are geographically disperse. Should one building lose power, you are still in business.



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GregoryF
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This is where we are confused - Why would anyone do Clustering at all?



Clustering provides quick failover, usually under one minute. With no changes for DNS (you connect to a virtual machine name, not a NetBIOS Server Name. Clustering also takes over all jobs/ logins, DTS packages, and is very low for administrative overhead.

If a cluster fail's over, there is not much that needs to be done (except examine what happened). Many times I have found that a cluster has failed over, and no one even knew it (yes, that means that the monitoring solution needs tweaking).

The most common solution these days is a cluster in your primary datacenter with log-shipping or mirroring to the backup data center.

I would also echo the comment that with as many databases that you have, clustering will be a breaze versus setting up the other solutions, but clustering won't protect you for losing for first DC (geographically dispersed clustering will, but that's a whole different animal)

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Lynn Pettis
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My concern with implementing mirroring is based on the 130 current databases and that this could easily grow. There may be latency issues trying to establish that many connections between two servers.

Cool
Lynn Pettis

For better assistance in answering your questions, click here
For tips to get better help with Performance Problems, click here
For Running Totals and its variations, click here or when working with partitioned tables
For more about Tally Tables, click here
For more about Cross Tabs and Pivots, click here and here
Managing Transaction Logs

SQL Musings from the Desert Fountain Valley SQL (My Mirror Blog)
SQLRNNR
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Unless absolutely necessary I would not mirror that many databases. I would pick and choose which databases were to be mirrored.



Jason AKA CirqueDeSQLeil
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vidya_pande
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Cluster is for quick failover for the server. You dont need to worry about logins, DBmail settings, and many other server level settings when you have cluster because it shares the same disk.

Cluster does not provide muti site redundency of the databases. If mutisite redundency of database is required then you need to have mirroring or log shipping.



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