We require guidance on server configuration for offering VDS hosting services using KVM technology.

Currently, we have the following hardware components:
- CPU: Core i7-3930k
- RAM: 64GB

We would appreciate answers to the following inquiries:
- Which HDD is recommended for local storage?
- Is it advisable to employ software RAID 10? If not, what RAID controller would you suggest?
- Would it be beneficial to have two separate storages, one on HDD and the other on SSD, to cater to different customer requirements?
- What is the approximate number of virtual servers that can be hosted with minimal overselling?

For local storage, a recommended option would be to use enterprise-grade HDDs such as WD Red Pro or Seagate IronWolf. These drives are designed for continuous operation and can provide good performance for VDS hosting.

Employing software RAID 10 is generally a good choice for data redundancy and performance improvement. It is recommended to use Linux Software RAID (mdadm) as it is widely supported and reliable. However, if you prefer a hardware RAID solution, a popular choice is the LSI MegaRAID series.

Having two separate storages, one on HDD and the other on SSD, can be beneficial for catering to different customer requirements. SSDs provide faster read/write speeds and better performance for certain workloads, while HDDs offer larger storage capacity at a lower cost. This allows you to provide flexibility in your hosting offerings and meet a wider range of customer needs.

The number of virtual servers you can host with minimal overselling will depend on various factors such as the resource requirements of each virtual server and the total resources available on your server. With a Core i7-3930k CPU and 64GB RAM, you should be able to comfortably host several virtual servers. However, the exact number will also depend on the specific resource allocation and usage patterns of your customers. It's important to monitor resource utilization and ensure that you have enough capacity to avoid performance degradation.

considerations for your server configuration for VDS hosting:

1. CPU: The Core i7-3930k is a good processor for hosting multiple virtual servers. It has six cores and 12 threads, which provides good multitasking capability. However, the number of virtual servers you can host will also depend on their CPU usage requirements.

2. RAM: With 64GB of RAM, you have a decent amount of memory to allocate to virtual servers. Make sure to allocate sufficient memory to each virtual server based on their requirements, and also consider leaving some buffer memory for the host operating system.

3. Storage Considerations:
  - HDDs: For local storage, enterprise-grade HDDs with high RPM (7200 or above) are recommended to ensure good performance and durability.
  - SSDs: If you choose to have separate storage on SSDs, they can significantly enhance performance for workloads that require fast disk access, such as databases or high-traffic websites.
  - Storage Capacity Planning: Consider the expected storage needs of your customers and plan accordingly. Running out of storage space can be a challenge, so it's important to monitor usage and plan for future growth.

4. RAID Configuration: RAID 10 (or RAID 1+0) is generally recommended for its combination of data redundancy and performance. It provides both mirroring and striping across multiple drives. Software RAID using mdadm is a reliable and cost-effective option, but if you prefer a hardware RAID solution, ensure it supports RAID 10 and has good compatibility with your server setup.

5. Virtual Server Density: The number of virtual servers you can host with minimal overselling will vary depending on the resource requirements of each customer and the total resources available. It's important to analyze the workload patterns and resource utilization of your virtual servers to ensure optimal performance without overselling resources.

6. Network Connectivity: Ensure that your server has sufficient network connectivity to handle the traffic generated by multiple virtual servers. Consider using a dedicated gigabit Ethernet connection or even a 10-gigabit connection if you expect high network traffic.

7. Virtualization Technology: Since you mentioned using KVM technology, it is a robust and widely used virtualization solution for Linux-based systems. Ensure that you have the necessary virtualization software and drivers installed on your server.

8. Resource Allocation: When hosting multiple virtual servers, it's essential to carefully allocate resources such as CPU cores, RAM, and storage to each virtual server. Consider using tools like cgroups or resource pooling to manage and distribute resources effectively among the virtual servers.

9. Backup and Disaster Recovery: Implement a reliable backup strategy to ensure data integrity and safeguard against data loss. Regularly back up both the host system and the virtual servers. Additionally, consider implementing a disaster recovery plan to quickly recover operations in case of hardware or software failures.

10. Security and Isolation: Ensure that your server setup provides strong isolation between virtual servers to prevent any unauthorized access or potential security breaches. Utilize security best practices, such as secure configurations, regular updates, and robust firewall settings, to protect both the host system and the virtual servers.

11. Monitoring and Management: Implement a monitoring and management system to keep track of system health, performance, and resource utilization. This will help you identify any bottlenecks or issues promptly and optimize resource allocation.

12. Scalability and Future Growth: As your VDS hosting services grow, consider the scalability of your server configuration. Plan for future expansion by ensuring that your hardware components, such as CPU and RAM, can be upgraded if needed. Additionally, consider implementing a distributed storage system or adding more servers to handle increased demand.

To begin with: In any case, there is no need to consider setting up VDS hosting for clients if you ask these kinds of questions! You will, at the very least, negatively affect your karma.
Your question reveals a lack of knowledge and experience, both of which will lead to numerous issues.

Experimenting "on cats" will help you grasp the advantages and disadvantages of different approaches, as well as gain some experience in resolving inevitable problems.

However, the idea of shifting the burden of your training onto clients, as you plan to do, is risky.

You can obtain the HDD that is compatible with RAID 10, which allows for better performance and security. Additionally, you have the flexibility to configure RAID-Z, a different type of storage configuration.

When it comes to storage, using two separate storages may not be the most effective solution. Instead, consider setting up an SSD as a disk cache, which is commonly used in contemporary SSD hosting. This can be achieved through the implementation of ARC ZFS.

As for the number of cores, it is generally determined by the system's specifications. However, depending on how you allocate and distribute the cores, you may have the option to increase their quantity.