How Does Local Storage Offer High Availability
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@scottalanmiller I was talking more on a virtual, local storage level. As I'm a VMware guy, I tend to steer towards their technologies. Didn't know about all those other offerings, though. Thanks for pointing them out!
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@antonit said:
As I'm a VMware guy, I tend to steer towards their technologies.
Think of the ecosystem like this... if someone offers it for VMware, it is probably built in to everything else. The degree to which VMware lacks the basics is mind boggling, especially when you find out it isn't free and everyone else is. It's not that the technology is bad, it isn't, it's excellent, it's just so amazingly lacking. The things that VMware can't do, like software RAID and Replicated Local Storage, that its competitors had from day one, over a decade ago, is crazy.
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I've read your article on the Inverted Pyramid of Doom (nice) in the past. I was thinking about something the other day when someone told me about their SAN having dual controllers, one for failover. But I cannot remember what you said about dual controllers... In a Mango thread sometime in the past, someone posted, "Well we have some redundancy, we have dual controllers." But you had commented, "Well dual controllers doesn't mean redundancy, because if one controller fails..." -bleh-. Can't remember how you finished a sentence like that. Help me out here? (The obvious thing here is that one box by itself is a single point of failure, regardless what kind of resources you put in it, it's still one box). But there was something specifically about a dual controller setup that sales people throw out there that you spoke to, and it was pretty killer.
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@BBigford Are you remembering those cases of fake duel controllers? What I mean by fake duel controllers is that some systems advertised duel controllers, but when one of the controllers went down it would take the other one with it as well. In those cases duel controllers actually made the system much less stable than a single controller would have. The one example I remember off the top of my head is Dell VRTX, but I know some SANs have had the same issue.
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@travisdh1 I do remember that one but I thought I had read SAM say something else. Maybe I'm just crazy. I'm probably crazy. It could very well have been that though. That feature was completely misleading and criminal to even put on a feature sheet.
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@BBigford said:
I've read your article on the Inverted Pyramid of Doom (nice) in the past. I was thinking about something the other day when someone told me about their SAN having dual controllers, one for failover. But I cannot remember what you said about dual controllers... In a Mango thread sometime in the past, someone posted, "Well we have some redundancy, we have dual controllers." But you had commented, "Well dual controllers doesn't mean redundancy, because if one controller fails..." -bleh-. Can't remember how you finished a sentence like that. Help me out here? (The obvious thing here is that one box by itself is a single point of failure, regardless what kind of resources you put in it, it's still one box). But there was something specifically about a dual controller setup that sales people throw out there that you spoke to, and it was pretty killer.
It's the straw house problem. Tightly couples controllers in a single box kill each other rather than protecting each other. If you have a fire coming, having redundant straw houses right next to each other for redundancy is pretty silly - not only will the same fire cause them both to burn, the fire at one house will set the next on fire.
And then the second problem.... it's just one component. Controllers don't normally fail. That's why it's the one thing not redundant in a normal server - because it is a pointless place to have redundancy because that's not how you get HA.
And the third problem - high end servers DO have redundant controllers, so the SAN having it only means that the SAN is "as good" as the server but since the SAN is external and extra, it is not better, it's worse.
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@travisdh1 said:
@BBigford Are you remembering those cases of fake duel controllers? What I mean by fake duel controllers is that some systems advertised duel controllers, but when one of the controllers went down it would take the other one with it as well. In those cases duel controllers actually made the system much less stable than a single controller would have. The one example I remember off the top of my head is Dell VRTX, but I know some SANs have had the same issue.
It's not a rare thing where an example has to be sought out. Every dual controller system under a certain price point and essentially all but a handful of vendors do the "tightly coupled" controllers. Every product in the SMB price range is that way.
HDS and EMC make a few true active/active controller units. But if you are buying them, you could have bought a dual controller server instead for cheaper and more power and more reliability. Even active/active doesn't make sense, it just makes it reliable as a single object.
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@BBigford said:
@travisdh1 I do remember that one but I thought I had read SAM say something else. Maybe I'm just crazy. I'm probably crazy. It could very well have been that though. That feature was completely misleading and criminal to even put on a feature sheet.
As long as they only called it redundant. Most IT people don't care about reliability, they just want redundancy. So why not sell it to them?
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@scottalanmiller said:
@BBigford said:
@travisdh1 I do remember that one but I thought I had read SAM say something else. Maybe I'm just crazy. I'm probably crazy. It could very well have been that though. That feature was completely misleading and criminal to even put on a feature sheet.
As long as they only called it redundant. Most IT people don't care about reliability, they just want redundancy. So why not sell it to them?
I can't remember if they were labeled as redundant and it being a straight up lie, or if they were marketed as dual controllers and it being implied, which is basically misleading...
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@BBigford said:
@scottalanmiller said:
@BBigford said:
@travisdh1 I do remember that one but I thought I had read SAM say something else. Maybe I'm just crazy. I'm probably crazy. It could very well have been that though. That feature was completely misleading and criminal to even put on a feature sheet.
As long as they only called it redundant. Most IT people don't care about reliability, they just want redundancy. So why not sell it to them?
I can't remember if they were labeled as redundant and it being a straight up lie, or if they were marketed as dual controllers and it being implied, which is basically misleading...
Redundant is the correct term. Redundant means nothing, it only means there are two of them. Like you have redundant seat belts in your car. Only one is useful, but it doesn't stop the term from being correct. In the UK, being redundant implies you are useless and being fired. The idea that redundant means more reliable is purely made up by IT people and is one of those things that IT does to aid marketers. The marketer says something useless, like redundant, and the IT person just assumes that the marketer meant to say reliable, so in their head they replace the term. But redundant suggests nothing of the sort. It's not lying in the least, the lie is that redundancy has value.
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They are truly dual controllers. There is nothing misleading. The only thing that would be misleading is if someone says that dual controllers and/or redundancy gives you high availability. That's the misleading part.
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@scottalanmiller said:
They are truly dual controllers. There is nothing misleading. The only thing that would be misleading is if someone says that dual controllers and/or redundancy gives you high availability. That's the misleading part.
When it really boils down, I think maybe the problem is not in the marketing, but in the assumption by the buyer about what they are receiving without asking all the qualifying questions.
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@BBigford said:
When it really boils down, I think maybe the problem is not in the marketing, but in the assumption by the buyer about what they are receiving without asking all the qualifying questions.
Yup. I help IT people with this all of the time. I hear it constantly. "But they told me this...." Then I say "Did they really? That would be lying, what did they actually say?"
Then it turns out, nearly every time, that the sales person said something factual, but not positive about the product. Then the IT person, certain that the sales person meant to say something positive, corrected what they said "in their head" and made it so that they heard something positive that was never stated or implied at all.
It's like a word problem, something else IT people often struggle with. Read many posted IT questions. If you look, you'll often see a question about an application configuration issue or a license mistake but they will post it to a virtualization forum and put a title that only mentions things that aren't related to the issue and have a huge description with the problem hidden in it.
Why do people do this? Because they are confused and cannot decipher what is and isn't relevant and what it means. It IT people so often have problems expressing what matters when they are the ones telling the problem, imagine what a problem it is when hearing a description!
All marketing has to do is say enough stuff, just random stuff, and the IT Pros will, much of the time, hear something close enough to something that they wanted to hear that they will fill in the gaps!
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Examples of negatives or neutrals that sales people use and IT people turn into positives....
It's Redundant:
IT Hears: It's highly reliable.
What it actually means: It costs more because you are double spending!It has a large ecosystem
IT Hears: It's so popular everyone makes software for it.
What it actually means: The product is so lacking in features that a market has sprung up fixing it!It's Closed Source
IT Hears: It comes with support.
What it actually means: You are a hostage to the vendor and their is no incentive to provide good support! -
@scottalanmiller said:
Examples of negatives or neutrals that sales people use and IT people turn into positives....
It's Redundant:
IT Hears: It's highly reliable.
What it actually means: It costs more because you are double spending!It has a large ecosystem
IT Hears: It's so popular everyone makes software for it.
What it actually means: The product is so lacking in features that a market has sprung up fixing it!It's Closed Source
IT Hears: It comes with support.
What it actually means: You are a hostage to the vendor and their is no incentive to provide good support!It's Closed Source: I definitely agree with you there.
It's Redudant: We're just talking about controllers still, right? (Thinking about clusters).
It has a large ecosystem: I didn't really understand that one, with the market springing up to fix it. A large ecosystem to me would mean there are tons of different devices available for development on the platform, and tons of development going on. Like OpenStack would be something I would call a fairly large ecosystem...
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@BBigford said:
It's Redudant: We're just talking about controllers still, right? (Thinking about clusters).
No, the term means "two of something". Nothing more. If you feel the term redundancy means something positive, there is a misunderstanding.
Redundancy isn't inherently bad, but it is also not inherently good. The term carries no such connotation.
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@BBigford said:
It has a large ecosystem: I didn't really understand that one, with the market springing up to fix it. A large ecosystem to me would mean there are tons of different devices available for development on the platform, and tons of development going on. Like OpenStack would be something I would call a fairly large ecosystem...
A good example is VMware. It is often sold as its key value being "a big ecosystem, tons of vendors make stuff for it."
Exactly, they need third party vendors to make their RAID for them, their backups for them, their storage replication for them, etc.
XenServer is then derided for having a small ecosystem. Conveniently the people making money selling VMware leave out that XenServer doesn't need one since all of the things that people make for VMware are built in to XenServer (RAID, DRBD, backup, etc.) Why would someone remake something that is already included?
It's like saying that you should buy Windows because of all the AV vendors and ignore Linux because it doesn't need them.
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@scottalanmiller said:
@BBigford said:
It's Redudant: We're just talking about controllers still, right? (Thinking about clusters).
No, the term means "two of something". Nothing more. If you feel the term redundancy means something positive, there is a misunderstanding.
Redundancy isn't inherently bad, but it is also not inherently good. The term carries no such connotation.
Ok, just wanted to make sure. I was hearing "two of something", obviously buying two of something is more than buying one of something though.
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@BBigford said:
Ok, just wanted to make sure. I was hearing "two of something", obviously buying two of something is more than buying one of something though.
Doesn't mean that you have a way for two of them to be better than one, though. Redundant bills, redundant outages... all bad things.
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Imagine if we applied it to something really silly, like licenses. I'll sell you "redundant Windows Server licenses." Literally, twice as many as you can use.
Sound good? No, of course not. And yet... that's actually better than dual controllers in most cases, because the double licenses is only a waste of money. But double controllers is often a waste of money AND they make the system more dangerous!
