RAID 10, 20 Disks, How Many Hot Spares
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@scottalanmiller Then we disagree on how much protection vs space/IOPS is warranted on a theoretical array. I see no value in wasting slots you paid a F(@*# ton of money for.
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@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
I disagree and would populate the array to as many drives as I could. Hot spares have little or no value in SMB space where it's on premises and you have easy access.
Hot spares and the SMB have no relationship. SMBs should be on premises the least, not the most. Combining mistakes doesn't make sense. You are making several assumptions that are wrong...
- That more IOPS are important enough to increase risk over past the point of the array being spec'd out already.
- That additional capacity has benefits beyond the specification point.
- That hot spares have no value, they always have some value in a mirrored array.
- That SMBs will be on premises.
All of those are wrong or potentially wrong. What we know in the OP's case is that the array was spec'd, now they are looking to invest in additional protection. Your recommendation is not just to invest, but to invest against protection and re-spec the array based on no data of the needs of the array at all. What if it is already way more IOPS and capacity than needed and any additional is just waste, but their risk aversion is high and the server is hosted on an island with no easy access?
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@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
@scottalanmiller Then we disagree on how much protection vs space/IOPS is warranted on a theoretical array.
No, you are having a discussion about protection vs space/IOPS and I am not. It's that simple. You are making a point that doesn't related to the question. The question is about investing in protection. You believe that "more capacity" is always better, even if there is no use for it?
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@scottalanmiller Argue a use case then, don't dance around making me chase you.
My use case is on prem easy access. Define yours and maybe we can agree on something.
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@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
I see no value in wasting slots you paid a F(@*# ton of money for.
No one said to waste them. They are talking about investing in additional protection.
Putting drives into the array when the IOPS and capacity are not needed is 100% wasted. So you just defeated your own point, there.
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@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
@scottalanmiller Argue a use case then, don't dance around making me chase you.
DOn't need a use case, risk aversion is the key. IOPS and capacity are spec'd properly, no more needed. Risk of the array is a concern. Hot spares would lower the risk, enlarging the array would increase the risk. This isn't complex. There is a goal: reducing risk. Your proposal is to undermine the goal for what reason? What makes you believe that risk protection is always bad and that higher risk is always good? Where would you stop with that logic? Always buy the biggest, fastest drives in the biggest possible arrays?
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@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
My use case is on prem easy access. Define yours and maybe we can agree on something.
- No one even suggested that on prem was going on, that's a totally false assumption. So you can't make up a use case and then use it to make the "it's always this way."
- Just because on prem is easy doesn't make off hours easy.
- Just because on prem is easy doesn't mean that wasting money on cold spares makes sense when hot spares are more reliable and less effort.
- Just because on prem is easy doesn't mean that we should increase risk for no known reason when the goal was to reduce risk.
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@scottalanmiller said in RAID 10, 20 Disks, How Many Hot Spares:
@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
@scottalanmiller Argue a use case then, don't dance around making me chase you.
DOn't need a use case, risk aversion is the key.
Bullshit, this is how you gish gallop all over anyone who disagrees with you - moving the goal posts. It's irritating as fuck tbh.
IOPS and capacity are spec'd properly, no more needed.
Again, this is crap - I know you can do better.
Give a real world example.
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@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
@scottalanmiller said in RAID 10, 20 Disks, How Many Hot Spares:
@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
@scottalanmiller Argue a use case then, don't dance around making me chase you.
DOn't need a use case, risk aversion is the key.
Bullshit, this is how you gish gallop all over anyone who disagrees with you - moving the goal posts. It's irritating as fuck tbh.
Sorry, but thats exactly what didn't happen. The goal never moved, at all. The goal was to reduce risk, you have a personal agenda that risk should never be reduced only increased and you are saying anything, including now making a personal attack, to support it. But you are not at all looking at the needs of the OP, just interjecting some personal goal that doesn't align.
No moving goal posts, none. You made up a new goal that didn't exist.
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@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
IOPS and capacity are spec'd properly, no more needed.
Again, this is crap - I know you can do better.
Give a real world example.
Not crap at all, it's how we do IT. You believe that "more is always better", no matter what. But only in IOPS and capacity, not in protection? By that logic, RAID 0 is always the best choice, right?
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@scottalanmiller said in RAID 10, 20 Disks, How Many Hot Spares:
@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
My use case is on prem easy access. Define yours and maybe we can agree on something.
- No one even suggested that on prem was going on, that's a totally false assumption. So you can't make up a use case and then use it to make the "it's always this way."
No one said it wasn't
- Just because on prem is easy doesn't make off hours easy.
It does in my case
- Just because on prem is easy doesn't mean that wasting money on cold spares makes sense when hot spares are more reliable and less effort.
Sure it does, in some circumstances - this is why you should define a use case so we can have a real discussion
- Just because on prem is easy doesn't mean that we should increase risk for no known reason when the goal was to reduce risk.
Sure it does. This is not a black and white case, there are shades of grey.
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Why do you need a scenario? We are past scenarios, we know the goal within the context which is to reduce risk. It's that simple. You are trying to make it complex so that you can take an arbitrary scenario and hope to shoot it down when we don't know the exact scenario, only the goal of risk reduction. Why are you so opposed to someone having a properly designed array for speed and capacity and considering lowering their risks? What's actually going on?
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@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
@scottalanmiller said in RAID 10, 20 Disks, How Many Hot Spares:
@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
My use case is on prem easy access. Define yours and maybe we can agree on something.
- No one even suggested that on prem was going on, that's a totally false assumption. So you can't make up a use case and then use it to make the "it's always this way."
No one said it wasn't
So because you inject your own details and no one specifically disputes them, they become true?
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@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
- Just because on prem is easy doesn't make off hours easy.
It does in my case
And your case is not in question, so this is a red herring.
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@scottalanmiller said in RAID 10, 20 Disks, How Many Hot Spares:
@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
@scottalanmiller said in RAID 10, 20 Disks, How Many Hot Spares:
@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
My use case is on prem easy access. Define yours and maybe we can agree on something.
- No one even suggested that on prem was going on, that's a totally false assumption. So you can't make up a use case and then use it to make the "it's always this way."
No one said it wasn't
So because you inject your own details and no one specifically disputes them, they become true?
That seems to be what you do
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@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
- Just because on prem is easy doesn't mean that wasting money on cold spares makes sense when hot spares are more reliable and less effort.
Sure it does, in some circumstances - this is why you should define a use case so we can have a real discussion
Nope, cold spares don't work that way. If you have that magic use case, you can provide it. I know of no case where cold spares are better than hot ones except when the array is full for other reasons (not the case here - so we have your example case right now) or where you need to share them between many arrays (no reason to inject that odd assumption here.)
There is zero need for a use case, we know the factors already. That you CAN come up with a use case where these things are not true based on changing the fundamental goals is totally non-applicable to the situation.
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@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
@scottalanmiller said in RAID 10, 20 Disks, How Many Hot Spares:
@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
@scottalanmiller said in RAID 10, 20 Disks, How Many Hot Spares:
@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
My use case is on prem easy access. Define yours and maybe we can agree on something.
- No one even suggested that on prem was going on, that's a totally false assumption. So you can't make up a use case and then use it to make the "it's always this way."
No one said it wasn't
So because you inject your own details and no one specifically disputes them, they become true?
That seems to be what you do
Okay, what detail did I interject? I'm working from the OP and nothing else. What have I added?
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@MattSpeller said in RAID 10, 20 Disks, How Many Hot Spares:
- Just because on prem is easy doesn't mean that we should increase risk for no known reason when the goal was to reduce risk.
Sure it does. This is not a black and white case, there are shades of grey.
Whoa, you just said that "sure it does" meaning it's black and white and is always one thing. Then you say that there are shades of grey . Which is it, it can't be both. I made the case that it wasn't black and white, you disagreed and then said I was right.
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The OP is asking about one thing... how many hot spares to add to data protection in an array of this size. That's it. There are zero questions about needing more capacity or performance. None, zero. There is no info on where the array is hosted, none. The question is about one thing... risk. Risk and only risk. How much risk reduction is generally recommended.
Obviously the OP didn't provide enough info for anything but general cases and general guidelines. But what we know from the asking of the question is that their concern is "how much do they need to lower their risk." That's the only thing that they are asking. They aren't asking how to "best use additional drives", if they needed more drives we can assume that they would have a larger array than they do and would be asking about how many hot spares on a larger array.
We don't know if hot spares make sense, we don't have enough details. We only know that they rarely make sense in a 20 disk RAID 10. We do know that hot spares are always better than cold spares if the slots are empty otherwise, unless the cold spares need to be shared to other chassis to save money. But that's it. And since the question is about a single array, not a group of arrays, we have to ignore the use case where cold spares are a consideration. We also know that there are at least two open slots or else the question could not be asked at all.
So given what we know about the question, we know that the possible answers are no hot spares, one or more hot spares, and that is all. If we start suggesting things like "buy drives but instead of using them as hot spares, make your array bigger" we change everything. Not only do we make wild, unfounded assumptions about their risk profile which we are not in a position to make whatsoever, but we also go a massive step farther and start to make assumptions about their best use case of money.
So now, not only do we suggest that they increase risk rather than lower it like they were trying to do (based on what I keep asking, we know nothing to give us this leniency) but we then also take the money that they might have invested in risk protection and suggest not that they use it "where the business can most use it" but suggest that the only possible use case for that money is to invest it in disks? We know nothing about the cost of those disks, the utility of those disks, the finances of the company, where that money could be spent and the valuation of different investment strategies.
In no way could we make that recommendation without knowing a lot more. What we can, and indeed the only thing that we can tell the OP is how hot spares react, what their investment percentage is, and how often or rarely they are applicable in this type of array and what factors may or may not make them more or less valuable.
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So you want a scenario? This is contrived and not mine to make but here we go...
- SMBs should basically always have their servers in colocation facilities. What SMB has the facilities to host their own properly? Datacenters charge for manual labor and don't always provide easy access for vendors. Having a hot spare in the datacenter can be instant recovery happening instead of waiting hours or days for the vendor to get in with spare parts (it means you can get NBD deals instead of 4 hour ones to save money) adding tons of protection for very little money. This grows significantly if you don't have a vendor doing the swaps but plan to do it yourself. NTG's travel time to our old datacenter was four hours, for example.
- Even in a datacenter, cold spares can take a long time to get put into place if the DC is busy, especially if things happen off hours. And there is risk that the wrong drive will be replaced, the server can't be found or whatever. Pay for a Tier IV and that stuff mostly goes away, but SMBs often are in lower tier DCs or do on premises and take risks that people will be less trained and make more mistakes.
- IT Pros often don't understand RAID and will power down a machine when the RAID needs a drive replaced. A lot of people tackle this in the real world when they aren't the sole IT guy and are forced to make systems that are as self healing as possible because they don't always know who is going to be doing the work, especially years in the future when the systems will be most likely to fail. It's an investment in better processes. So even simple on premises systems have reasons why it can make sense.
- Many SMBs don't have full time IT staff, that alone explains everything.
- Many SMBs don't have on premises IT staff, again, totally explains it.
- Many SMBs have fewer IT staff than they have physical locations.
- MSPs often are not given blanket access to customer facilities and need to provide rapid protection faster than a customer may reliably be able to provide physical access.
- Systems in remote locations do not always have reliable supply chains, especially outside of the US. Whether you are on an island in Lake Superior, in Matagalpa Nicaragua, on a cruise ship, in a research station on a mountain or in a state that gets way too much snow, hurricanes or flooding... having hot spares that can take care of things when staff and/or supply chains cannot get drives swapped promptly can be absolutely critical.
- Many SMBs run without IT staff and need systems to be as self healing as possible.
