Virtual Server Hardware Requirements
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This article is for people and companies that decided to build or upgrade their IT infrastructure for virtualization. I'll provide some advice on how to choose a physical server, but I won't delve deep into software.
Virtualization hardware is as important as software. Hardware defines the flexibility and performance of your infrastructure, consolidation coefficient, efficiency, TCO and business application accessibility. Irrelevant solutions decrease profitability and limit your freedom of action.
And we don't need that.
“Server” in a shoe box. No comments.
To save money, many companies convert their equipment initially purchased for other purposes: PCs or old servers. This approach, however, has many disadvantages:
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PCs are not intended for uninterrupted service of many users,
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PCs and servers purchased for other purposes may not be suitable for further vertical scaling (you won't be able to replace the components or add resources),
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Low-powered CPU and limited storage decrease VM performance,
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Limited CPU decreases the maximum amount of VMs.
To start, you need to carefully plan your task, define what server you need, and only then evaluate whether your equipment fits. Testing helps to find weak spots within a week or a month.
Virtualization Server Hardware Guide
Dell bare metal server
Virtualization server should be suitable for vertical scaling. For example, you'll be able to install a second CPU, add several disks, RAM sticks, or another network card in the expansion slot.
Low-budget models are not that vertically scalable. That's why the best server for virtualization is a medium-level 2U (or above) model. If possible, a model within two last generations. Also, modern 1U servers with an SSD would do just fine.
The performance of a VM is defined by four parameters: CPU, RAM, disk subsystem, network adapter.
Virtual Server CPU Requirements
There are two key figures on the market: Intel and AMD. In terms of performance, when we compare CPUs of the same price range, they are almost identical. Within several generations each vendor grabs the biggest piece of the pie. New series are released all the time, and we need to test them to single out the leader. In some tasks and tests, Intel is better, and in others — AMD. The comparison reminds of the holy battles of Cupertino between Android and iOS users.
IMPORTANT! There are more models based on Intel CPUs, including refurbished ones that have more attractive prices without sacrificing reliability. Recently, Intel was far ahead of the corporate field, meaning AMD had less models in previous generations. Now the scales are almost even, but you need to consider software optimization and developer recommendations.
As for the latest generations, AMD has created a rather interesting page where you can compare the TCO of server virtualization using Intel Scalable and AMD EPYC. Intel is not the winner there, but what else would you expect on a competitor's website :) Still, in the latest generations, EPYC CPUs are actually a great balance between the price and performance.
To implement hardware acceleration of virtualization, competing vendors have developed proprietary technologies that were developed using different methods but have pretty much the same functions:
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AMD offers the users AMD-V (Virtualization Technology), Vi;
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And Intel offers similar technology called Intel VT (Virtualization Technology), VT-x, VT-d and VT-c.
So, if the situation is pretty much similar for both vendors, what should you choose?
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A piece of advice on choosing a CPU brand: choose the brand you already use for your IT infrastructure. As a rule, single-brand systems operate better because of high compatibility. However, your virtualization should be based on the functions you need, not the brand.
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Advice on CPU specifications: if the space you plan to use for IT infrastructure is limited, you should choose CPUs with many cores and high clock rate. Keep in mind that those are more expensive and subject to heating. If the priority is the VM performance, then clock rate prevails over cores. The more cores you have, the more VMs you can implement.
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Advice on vCPU (virtual CPU with 1 core) division: a standard rule used by all administrators — 1 vCPU per 1 VM. Don't implement too many vCPUs per a VM. First of all, this way you'll limit yourself in the amount of VMs per a physical server. Second of all, you need to carry out tests that'll show whether an application actually requires that many cores and uses processing powers constantly. For instance, SQL servers require more cores than e-mail, file or RADIUS servers.
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Advice on VM testing: in a week/month you'll obtain certain trends and peak loads that show vulnerabilities. Testing prevents high competition for a core, memory, network, etc. Also, tests show you CPUs with low loads (so you can deploy more VMs on a host).
Virtual Server RAM Requirements
A server should have enough RAM for an OS/hypervisor, each VM and application. Virtualization requires a lot of RAM. Plus, you should have 30% reserve (or even more).
Advice on choosing server RAM: server manufacturers define/approve certain RAM vendors. It's almost impossible to install a random RAM stick and make it work. The choice is limited, so you can't let yourself go. Besides, sticks from different manufacturers are pretty much identical. It's about the price, compatibility and reliability (some manufacturers provide life-time warranty). So, the vendor is not the priority when it comes to RAM. At least not as high as for CPUs.
6 questions checklist before purchasing server RAM:
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DDR3 or DDR4? In the end of 2021, manufacturers started to switch to DDR5, so I wouldn't recommend DDR3,
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How many DRAM slots does your motherboard have?
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How many CPUs will you use, and how much memory do they support?
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Will the modules be installed in twos, threes or fours?
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What's the RAM frequency?
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RDIMM or LRDIMM?
The seven point should be RAM capacity, but the difference per virtual load is so big that there is no “one-fits-all” recommendation. The main part is to avoid memory shortage. Otherwise, “memory-short” VMs will seek from a drive, and that limits the OS and application performance. So, 30% reserve is a must for a hypervisor to dynamically allocate available RAM between VMs within limits.
Advice on vRAM allocation: even if your host machine has large RAM capacity, you shouldn't allocate it to VMs more than required. Carry out tests to define the actual capacity required by a user and/or applications. For basic users who work with office applications (such as Windows 10 and MS Office package), 4–5 GB RAM would be enough. If you allocate them 16 GB, there will be no difference.
Virtual Server Drive Requirements
Of course, SSDs are the best options for virtualization thanks to their low latency and high speed, especially in the tasks with high demands to disk subsystems (such as high-load databases). However, the price of an SSD is an issue. Some standard SAS HDDs are great if your budget is limited and if you build a RAID array with an increased reading rate.
Advice on drive types:
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Do not use SATA HDD for virtualization — the performance is not enough for many modern tasks. The only scenario for using SATA HDD: your tasks are not demanding in terms of reading/writing rate, and you have spare SATA HDDs in your server room. RAID 10, 30 or 50 will balance the speed,
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Choose something specific: SSD or SAS HDD. No need to mix it up. Some companies purchase SSDs for host OS and HDDs for guest ones. That would be a good solution to high performance/low expense type tasks. But that's not the case for us. A quick host SSD would be just waiting while slow VM HDDs carry out their input/output operations.
Virtual Server Network Adapter
It doesn't matter whether you use a local, hybrid or global network: a network adapter with 1 Gbps port may become a bottleneck. To achieve high performance and speed, you should use adapters with 2 or 4 ports. In 90% of the cases 1 Gbps would be enough, but if your loads require huge speed, consider a 10 Gbps adapter.
Advice on fail-safety: you can use one network adapter for non-critical VMs and small installations, but keep in mind that one adapter is one point of failure. If you plan to make your critical VMs highly accessible, you need another adapter for reserve.
Conclusion
In this article, I focused on a physical server for virtualization, but software is also an important aspect. However, the topic is so broad that it wouldn't be possible to cover it in the article.
Conclusion: hosting is not for everyone, so companies use their own servers for virtualization. For that, some companies adapt their existing infrastructures. Either it initially didn't fit the purpose, or became obsolete over time. And that's a problem.
If you can't afford new servers, you can save money and purchase refurbished Dell, HPE and Lenovo servers. They are 30% cheaper, but still highly effective and reliable. Plus, we'll provide you with a five-year warranty. Got questions left? Contact our managers