SAN in an Inverted Pyramid Architecture for Fourteen Physical Servers
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@dafyre said:
That would increase the number of Guest VMs he currently is operating.
VMs are irrelevant to SAN discussions. It is physical hosts alone that are the determining factor. VMs are a red herring.
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@dafyre said:
Let's assume you meant to write hosts instead of guests.
I meant physical guests of the SAN, not talking about virtualization or VMs in any way in this discussion.
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@dafyre said:
Okay, so he goes from 14 physical servers down to 12 physical servers. However, to build his (2-node) SAN, and take steps towards redundancy, he's only having to buy hard drives, instead of a full-boat SAN system from a vendor.
So this is built on the assumption that he can consolidate and that the 14 servers are not needed. The thing is, the idea of using the SAN only makes sense if he can't consolidate and so this would not be an option. If he can consolidate then we are in a completely different discussion.
Two servers as a SAN cluster is definitely an option. But be aware that you will need to replicate the disks so it is buying twice the disks and assumes that his current machines have the necessary storage capacity do to double storage duty. A single SAN approach is only 1x the disk purchase and it is specifically the cost reduction of the storage that makes a SAN viable. He does not have replicated storage today, the assumption is that he does not need it tomorrow.
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@dafyre said:
So we're looking at Let's go crazy and say $5,000 worth of hard drives (split evenly in his 2 servers that were taken for storage). That would still be a far cry cheaper than having to purchase 2 x Nimble SAN units for replication.
$5,000 is probably low, but we have no idea. But for enterprise drives, which is probably what we would be using, that's only 10 - 20 drives total. Since we need to replicate that's likely low.
No need for dual enterprise SAN. Going to dual enterprise SAN is assuming a need for HA which cannot be achieved with any of the other assumptions in this thread (need for 14 hosts) since you'd have HA storage and no HA elsewhere. So we are looking only at a single SAN here.
So yes, a single SAN is $30K+. But we are assuming no consolidation ability (or the 14 servers count is the issue) and no need for HA (or we have other issues that can't be addressed here anyway without buying more servers.)
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Ah, OK. I read that as guest = VM, lol. To me we are talking about both, as the shared storage would primarily be for his Hyper-V servers (thus my confusion on the term guest).
That being said, I still would stand by my Win/Win statement because it gets him closer to where he wants to be in moving towards redundancy. It makes it a good business decision because the cost of the hard drives would be negligible as long as he already has 2 servers that can be recycled as StarWind nodes (especially when compared with the cost of 2 x SAN units in Network Raid 1).
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@dafyre said:
To me we are talking about both, as the shared storage would primarily be for his Hyper-V servers (thus my confusion on the term guest).
The "shared" storage is for EVERY physical box no matter what role it plays because it is by having so many physical boxes no longer needing their own storage that you get cost savings.
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@dafyre said:
That being said, I still would stand by my Win/Win statement because it gets him closer to where he wants to be in moving towards redundancy. It makes it a good business decision because the cost of the hard drives would be negligible as long as he already has 2 servers that can be recycled as StarWind nodes (especially when compared with the cost of 2 x SAN units in Network Raid 1).
This only is viable if you also assume that the basic premise, that of needing 14 servers, is wrong. Starting with the "question is wrong" as a way to get to an answer is never right. I get what you are saying, but this thread is based on SAN for 14 servers, not SAN for 12 servers when we have two unused storage servers available.
Like I said, if we can assume that 14 servers are not necessary then none of this SAN discussion makes sense at all. You have to assume that 14 servers is the necessity.
So for your example you would need two new servers at a minimum of $5K each (likely) plus the disks to go in them. So that is $15K suddenly rather than $5K A 300% jump. And I still feel that $5K of drives is likely very low but let's go with it, it is likely close.
Then we have a minimum of $1,500 in Windows licensing to get to use Starwind. So we are up to $16.5K. Still nowhere near $30K for an enterprise SAN, but you can see how the numbers are much closer.
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Not knowing the capacity or IOPS numbers makes this a lot harder to hypothesize.
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@scottalanmiller said:
So yes, a single SAN is $30K+. But we are assuming no consolidation ability (or the 14 servers count is the issue) and no need for HA (or we have other issues that can't be addressed here anyway without buying more servers.)
So where is the savings with a $30K SAN? Not to mention the dedicated 1 Gb switch (actually at least two of them) if not 10 Gb switches or FC switches. oh and the adapters for that.
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@Dashrender said:
So where is the savings with a $30K SAN? Not to mention the dedicated 1 Gb switch (actually at least two of them) if not 10 Gb switches or FC switches. oh and the adapters for that.
Well let's do some standard math and see where we fall. We have to make some assumptions, of course, but for the point of the scenario....
It is all about wasted capacity. How much is in each server? Let's say each has 6x 1TB drives in RAID 6. That's 4TB usable in each host. So 84 drives purchased with 56TB usable.
1/3rd of all drives are for parity. Performance is split up between 14 hosts.
Now how much capacity are we likely using? Chances are a huge percentage is wasted on each server. Typically we use less than half. Chances are we could get by with something like 20TB usable on RAID 6 on a single SAN. And the machines get to split the performance.
A single 24TB SAN might be cheaper than 84TB of raw storage across all boxes while still being just as flexible. That's where the potential cost savings come from and why SANs require a lot of physical hosts connected to them to begin to pay off - it is about getting to a scale where the drives become cheaper through a combination of thin provisioning, storage consolidation and better RAID overhead.
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Ok, that works if and when it's time to replace a huge percentage of that storage all at once, otherwise you're needing to spend a rather substantial CapEx and wasting the remaining life of the old but not obsolete equipment. I suppose you could sell it and recoup some of that expense, but assuming he keeps the servers and only sells the HD's, what kinda return can he really expect on those?
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@Dashrender said:
Ok, that works if and when it's time to replace a huge percentage of that storage all at once, otherwise you're needing to spend a rather substantial CapEx and wasting the remaining life of the old but not obsolete equipment.
The other choice is repeatedly investing in technical debt. It remains substantial CapEx in both cases, one is just lower and "at once" instead of larger and "spread out."
It's why good design before purchase is so important, the technical debt component that is often overlooked is often crippling.
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@scottalanmiller said:
@Dashrender said:
Ok, that works if and when it's time to replace a huge percentage of that storage all at once, otherwise you're needing to spend a rather substantial CapEx and wasting the remaining life of the old but not obsolete equipment.
The other choice is repeatedly investing in technical debt. It remains substantial CapEx in both cases, one is just lower and "at once" instead of larger and "spread out."
It's why good design before purchase is so important, the technical debt component that is often overlooked is often crippling.
Very true, but the organic growth of many business also makes this difficult at best.
You also didn't mention the network infrastructure and adapters needed to run the SAN in your cost analysis, but I'm sure you didn't forget them.
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@Dashrender said:
You also didn't mention the network infrastructure and adapters needed to run the SAN in your cost analysis, but I'm sure you didn't forget them.
For 14 hosts you typically have a lot of options and not very expensive ones. Lower end GigE switches will normally do the trick just fine. It is a relatively minor cost in most cases where we are not talking about extreme HA but just "SA" IPOD setups.
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@Dashrender said:
Very true, but the organic growth of many business also makes this difficult at best.
When you get to 14 physical servers you might be past the point of claiming organic growth planning
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Here is a little bit more information about the environment. Also, when it comes to budget, I have none. We are a 6 person shop mainly offering consulting services in the ERP arena to customers that have on premise infrastructure in place.
I have 14 physical servers, which I mentioned many are Hyper-V hosts. Not all of them are however. So here is a list:
Physical
1 - 7 are virtual host servers ( 84 virtual machines)
8. Dedicated backup server (in house stuff)
9. Dedicated backup (for client)
9. Dedicated SQL (for client)
10. Replica Server (in house)
11. Replica Server (for client)
12. Physical remote DC
13. Remote backup repository
14. Hot spare server - (parts).The VMs are virtual desktops, application servers for a couple clients, domain controllers, remote desktop services servers, and file servers)
Most of these are Dell R710s with a couple R620s and 1 R720 (mostly older stuff that was refreshed 3 or so years ago and was picked up refurbed) - all with internal storage and a mish mash of different raid controllers.
As mentioned above, we have been lucky so far and haven't had anything major break, because with the VM density on a couple hosts and the roles the VMs play would be a significant hit. Not to mention everything is out of warranty and there is no maintenance in place for the hardware. Does that make a good case for HA? It seems too.
Ideally, I would like to consolidate a lot of this, and undo some of the funky setup that exists. For instance, having a standalone server for the accounting data, (with it own domain, rds, virtual desktops) separate from the rest of the the network. For whatever reason, someone thought it was a good idea to just separate everything out by creating a new domain! We need a development , lets just create a new domain for that!
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@Carnival-Boy said:
@scottalanmiller said:
more reliable than an average server making the use of just one actually not much of a risk
When the SAN fails you lose access to ALL your business applications. Whereas if one of his servers fails he only loses access to 13/14 of his business applications (about 7%).
Not if you have replicated SANs.
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@Jason said:
@Carnival-Boy said:
@scottalanmiller said:
more reliable than an average server making the use of just one actually not much of a risk
When the SAN fails you lose access to ALL your business applications. Whereas if one of his servers fails he only loses access to 13/14 of his business applications (about 7%).
Not if you have replicated SANs.
The point here was (according to Scott) that the OP wouldn't have replicated SANs because they don't have a need for HA. They would be going to a SAN for cost savings reasons, little to nothing more.
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But before that conversation can really continue, the OP should have a DPack ran on his current setup and see if consolidation of his current workloads is possible, how much storage he can, if any, give up and then see if a SAN still makes sense?
