April 9, 2010 at 2:35 pm
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.
April 9, 2010 at 2:56 pm
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.
April 9, 2010 at 3:38 pm
Thanks.
Could you expand on your reasons.
April 9, 2010 at 3:53 pm
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.
April 9, 2010 at 3:57 pm
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?
April 9, 2010 at 4:02 pm
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.
Jason...AKA CirqueDeSQLeil
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April 9, 2010 at 4:26 pm
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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April 9, 2010 at 8:45 pm
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.
April 9, 2010 at 8:53 pm
Unless absolutely necessary I would not mirror that many databases. I would pick and choose which databases were to be mirrored.
Jason...AKA CirqueDeSQLeil
_______________________________________________
I have given a name to my pain...MCM SQL Server, MVP
SQL RNNR
Posting Performance Based Questions - Gail Shaw[/url]
Learn Extended Events
April 10, 2010 at 11:28 am
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.
April 10, 2010 at 2:56 pm
CirquedeSQLeil (4/9/2010)
Unless absolutely necessary I would not mirror that many databases. I would pick and choose which databases were to be mirrored.
Maybe 10-20 percent are not used hourly, the rest are high use and need a fail over.
April 10, 2010 at 3:02 pm
The concern on cluster is we have the one device (the external Hard Drive Unit) as a fail point. It seems to be just a fancy piece of hardware that is just as likely to fail as any other server. So I my eyes a cluster is not safer than a single server. Where mirror I have a safe guard that if the Hard Drive fails in the main unit I can have the witness server move the traffic to the mirrored server.
We are log shipping to a secondary location.
April 10, 2010 at 3:27 pm
That's really dependent on your external drive source. If you just throw on and external drive bank via iSCSi with no redundancy or anything, then you're right.
That's why most people use SAN's that have redundancy, large caches, considerable battery power, and well-thought out RAID arrays that provide redundancy and performance. That's not to say that all SAN's are great. A poorly configured SAN can be just as bad as any thing else.
So if you are just planning to stick a cheap network drive array on the servers, maybe clustering is not the best option. I would spend my money on a better drive system before I start throwing more servers into the mix.
April 10, 2010 at 11:16 pm
In addition to what Robert said, keep in mind that Mirroring or Clustering are really only a piece of the big picture for DR.
Others have suggested a cluster that is mirrored. There is also geographic clustering. Then you add a SAN into the mix which has redundancy. Now throw in backups. There is also a design for backups to be considered for retention of those backups and storage location. Backups have also evolved to being able to be redundant as well - providing better DR for your company.
Jason...AKA CirqueDeSQLeil
_______________________________________________
I have given a name to my pain...MCM SQL Server, MVP
SQL RNNR
Posting Performance Based Questions - Gail Shaw[/url]
Learn Extended Events
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