Understanding Server 2012r2 Clustering
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100% personal and just doing this to learn.
All gets blown away when the trials end
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@Sparkum said:
100% personal and just doing this to learn.
All gets blown away when the trials end
OH, ok. Makes more sense then.
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Microsoft has some great free labs and training on 2012 R2 clustering. This helped me out big time when I was taking my MCSA tests.
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Their online education has gotten really good.
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Oh I'll check those out thanks!
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Just remember that this "lab" case, for Exchange DAG, is not using Windows clustering but is its own application level clustering. So this clustering stuff is for a different use case.
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@scottalanmiller -- Just so I understand... In most cases, Application Level Clustering > Windows Failover Clustering ?
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@dafyre said:
@scottalanmiller -- Just so I understand... In most cases, Application Level Clustering > Windows Failover Clustering ?
Probably in all cases but there must be one where this isn't true. But conceptually, application level clustering is the only way to get true, completely reliable failover (when done right.) Anything else is an attempt to make up for lacking application clustering. Windows Failover, VMware failover, etc. are all "making do", not ideal.
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Exchange is one time you should never use a SAN. Nor can you use Vmotion with Exchange. If you are running Exchange on site most of the time you might as well look at separate physical boxes but, then that comes down too why are you looking at exchange onsite vs hosted?
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@thecreativeone91 said:
Exchange is one time you should never use a SAN. Nor can you use Vmotion with Exchange. If you are running Exchange on site most of the time you might as well look at separate physical boxes but, then that comes down too why are you looking at exchange onsite vs hosted?
Other times include MS SQL Server (or pretty much any database), Active Directory, etc. Anything that has an open data connection.
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The times that SAN can be used for a reliably consistent failover are actually pretty rare and almost always cases where there was an easy way to have done it without a SAN.
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@scottalanmiller I would argue that about MSSQL and MySQL. We ran those on the Same box (as part of the same cluster) for a number of years. The only minor issue that would happen is that the SIS that the Campus used would throw an error message and wouldn't automatically reconnect. The error message I can understand. But not automatically reconnecting? That is an application issue and not a problem with Failover.
Our MySQL applications never had this problem.
We were probably just lucky, but we never lost any data in MSSQL Server due to a failover event.
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@dafyre said:
@scottalanmiller I would argue that about MSSQL and MySQL. We ran those on the Same box (as part of the same cluster) for a number of years. The only minor issue that would happen is that the SIS that the Campus used would throw an error message and wouldn't automatically reconnect. The error message I can understand. But not automatically reconnecting? That is an application issue and not a problem with Failover.
Our MySQL applications never had this problem.
We were probably just lucky, but we never lost any data in MSSQL Server due to a failover event.
MS SQL Server, MySQL, MariaDB, Oracle DB, PostgreSQL, DB2, Sybase... you name it. They can't survive having their storage ripped out from under them. SAN = violent storage ripping.
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Server 2012 Has safeguards in place. It's fine to run DCs on a SAN and use vMotion with Server 2012 or newer. The VM Generation ID is there for this reason. Even Cloning of DCs is now supported and if done properly will not cause USN issues.
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@thecreativeone91 said:
Exchange is one time you should never use a SAN. Nor can you use Vmotion with Exchange. If you are running Exchange on site most of the time you might as well look at separate physical boxes but, then that comes down too why are you looking at exchange onsite vs hosted?
I never knew this. What's the problem with Vmotion and/or failover with Exchange? What's the problem with SQL Server?
Not that I have a SAN or HA, I'm just interested. I was interested at the time I considered a SAN (a few years ago) by the fact that my reseller recommend against DAGs on the grounds of cost (additional licencing) and complexity, but recommended in favour of a SAN (which also has additional costs and complexity). At the time I couldn't understand their reasoning. I was always more inclined towards application level clustering - it just seemed to make more sense.
Exchange and SQL Server are both designed to recover from a crash. At worst, shouldn't failover be at least as good as a crash consistent recovery?
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@Carnival-Boy said:
I never knew this. What's the problem with Vmotion and/or failover with Exchange? What's the
problem with SQL Server?The problem is the state of the open files and open connections.
Exchange and SQL Server are both designed to recover from a crash. At worst, shouldn't failover be at least as good as a crash consistent recovery?
Yes, but vMotion/Live Migration is something you do that is not a crash scenario. It is a day to day business process.
Paid versions of Veeam have options to be aware of items in the guest and can easily move these types of services as ling as you know that any data from an open connection may get lost. Conveniently, most connections are simultaneous calls to the database and closed again. Only poorly designed applications anymore hold connections open.
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Of course they recommended a SAN, they make a ton of money off the sale, conversely they barely make anything selling you multiple copies of Exchange for the DAGs.
I'm wondering when or if we'll see MSPs, move away from the bad recommendations SANs anytime soon?
I had a friend who started at a small school district, they needed a new server. Their vendor/local computer shop sold them a one box VM host with a SAN. When he told me that I freaked out on him... told him why this was a horrible solution - he didn't seem to care. "It's to late" he said, "It's already done and installed and working."
Even now when I talk to him he doesn't seem to understand why this is bad.
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@Dashrender said:
Of course they recommended a SAN, they make a ton of money off the sale, conversely they barely make anything selling you multiple copies of Exchange for the DAGs.
soon?^^^ Cannot be overstated. Sales people are paid, by you, you sell the things that make them money. Not that they won't sell you other things, but when you are talking about something that is orders of magnitude more money in profits for them, you can't expect them to voluntarily do engineering work that you are not paying them for instead of selling you the high margin item that you are paying them for.
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@Dashrender said:
I'm wondering when or if we'll see MSPs, move away from the bad recommendations SANs anytime soon?
This is never going to be something that VARs (not MSPs) will change voluntarily. This is something that has always been driven by the customers. Only when the customers start paying for advice and not trying to get free advice lumped in with sales will this change. Most VARs are exclusively compensated by selling high margin solutions, they are not paid to provide good advice. If we ask for free advice, someone has to pay for that advice. So we, as the customers, determine by trying to get free advice which solutions the VAR will be paid for and which they will not.
Customers choose how their vendors are engaged. Vendors can choose not to work with customers in a certain manner, but the customer will always find a sales person willing to make a sale. As long as customers work that way, companies will exist to support that desire.
